Standing on a ledge 1,353ft in the air, looking down at the skyscrapers of bustling Chicago below, was one of those moments.
'Just step out, it's easy' I heard the guide urge. Perhaps so but the electrical signal which directed my legs had become stuck somewhere on its journey from my brain.
Peering out onto the world's most terrifying glass balcony from the top of the Willis (formerly Sears) Tower, my overwhelming desire was to remain rooted to the spot thank you very much.
And then the loss-of-face override kicked in. As images flashed up on screens around me of kids laughing and joking as they skipped care free across the glass floor, I gave myself a talking to and stepped forward.
Clinging on to the side - as if that would stop my plummet to the ground - I put one foot gingerly out onto the precarious platform. With no audible crack, I moved the second into position, then stepped forward. It was the most bizarre experience, my pride at my 'achievement' being only slightly dampened by another image of a pre-school child who appeared to be doing a handstand.
By the end of my session at The Ledge at Skydeck Chicago, I had sat, jumped, lain down face first, hopped around, as all the while Chicago life continued 103 storeys below. And I had the souvenir picture to prove it.
What it did, as well as make a 45-year-old feel better about themselves, was offer a unique perspective on an incredible city. One which I had enjoyed from the ground up, neck constantly craned skywards in the previous four days.
The architecture of the Windy City - apparently not so named because of the weather but for the hot air expounded by its politicians - leaves you breathless. Constantly surprising and awe-inspiring, each building seemingly trying to outdo the last in grandeur and boldness of design. All fitting together perfectly into a skyscraper patchwork of the modern, historic, art deco, and the downright bonkers.
First the very potted history. America's third most populous city on the shores of Lake Michigan grew rapidly in the 19th century as an important transportation hub between east and west.
Then there was the Great Chicago Fire in 1871 which destroyed a four square mile area and 17,000 mainly wooden framed buildings - apparently started by a cow kicking over a lantern on Mrs O'Leary's farm (a fiercely contested theory with efforts to clear the cow's name continuing). Much like the Great Fire of London what this appalling tragedy did was provide a blank canvas to create modern Chicago from the ashes.
Buildings sprang up using pioneering steel and stone construction, including the world's first skyscraper in 1885.
Based on Paris, the wide boulevards create a city which is never suffocating and always moving, allowing the elevated subway system (the L) to run high above the roadway without condemning the streets below to eternal darkness.
My first visit to Chicago began in the centrepiece of life in the city - the Chicago River. An ideal place to start for the first-time visitor is the Chicago Architecture Foundation Center River Cruise, a great way of finding your bearings in a sprawling metropolis. Wrap up warm if you decide, as I did, to take this particular journey in October as the temperature out on the water dips below that on the street as you journey along the wind tunnel river.
The experienced guide - a volunteer from the CAFC - talked us through a 75-minute cruise throwing more facts than I could ever hope to remember but highlighting every point of interest along the way. From the great fire to the first skyscraper, the classic early Wrigley and Chicago Tribune buildings, to the weirdly compelling 'corncob' towers, and on to the pioneering modern architecture, our guide's passion for her subject made it a truly captivating journey. Demonstrated perhaps by the fact only a few bailed out to the warm bar below deck before the end of the lecture. All, incredibly, delivered without notes.
Stepping off the boat, a visit to the Chicago Architecture Center itself (free with the boat ticket) was then a must to soak up more history of the city and learn how it continues to evolve. Armed with that knowledge, I was ready to step out and explore on foot.
Chicago is a vast city but the downtown area is also very walkable. I was staying at the newly-opened luxury LaSalle Chicago on South LaSalle Street, a boutique Marriott hotel with lashings of style, located in a recently renovated 100-year-old building right next to the imposing Chicago Board of Trade offices (recognisable to Batman fans as an iconic Gotham City location in the Dark Knight). My ridiculously spacious room on the 20th floor had a view out across Downtown. The hotel occupies four floors of the humongous building, the reception being on the 21st, along with an excellent restaurant 'the Grill on 21' where the portion sizes are, like the rest of the US, at least double what you expect. There is also a gym to work off your breakfast but I chose to hit the streets instead.
Even in the early morning, the streets feel alive but never as crowded as the likes of London or New York, allowing you to drink in the sights, sounds and smells of Chicago life.
Within a mile of my hotel I found the tranquillity of Millennium Park with its imposing Cloud Gate sculpture, known to most as The Bean. It is made up of 168 stainless steel plates welded together, with its highly polished exterior reflecting and distorting the city skyline. Also nearby and demanding a visit were the Art Institute of Chicago, the Museum of Contemporary Art, and aforementioned Willis Tower.
A little further took me to the shores of Lake Michigan and the funfair attractions along Navy Pier, as well as the Museum Campus - a 57-acre museum park which includes the Adler Planetarium; the Shedd Aquarium; and the Field Museum of Natural History, as well as Soldier Field, the home of the Chicago Bears American football team.
Back towards town, and I ended on the famous Magnificent Mile, the number one shopping destination filled with mid and high-end retailers, perfect for a bit of window shopping even if the current exchange rate did not allow many purchases.
All that walking certainly works up an appetite - which is not a problem in Chicago. An absolute must dos is the famous deep dish pizza which I sampled at Lou Malnati’s. I’m told Grandpa Malnati helped create Chicago’s first deep dish pizzeria in 1943 so it is a pretty safe bet.
Again, keep in mind the portion size and reduce by half when ordering. Other stops included a fantastic Greek meal at Avli River North, and classic Italian style of Alla Vita, both of which are very much worth a visit.
By evening, the city transforms again - known for its bustling theatre and concert scene with something for every taste. A visit to the renowned Kingston Mines Blues Club is recommended as is the brilliant Second City comedy club - the stage where the likes of Tina Fey, Stephen Colbert, and Steve Carell made their names.
Stepping out into the crisp evening air, my eyes again turned skywards. Whether standing on the street gazing up or peering down from 103 floors up through a glass floor, it is a truly unforgettable city from every angle.
I visited courtesy of www.choosechicago.com – a great place to go to plan your trip
I flew from Glasgow to Dublin to Chicago with Aer Lingus, which has the added bonus of clearing US customs in Ireland https://www.aerlingus.com/
My stay was at the luxury LaSalle Chicago, Autograph Collection https://thelasallechicago.com/