The hardest part is getting started. That’s true of many things, but especially applies to throwing yourself down the side of a skyscraper.

I learned this at the Philadelphia Outward Bound Building Adventure. I’d reported on the annual event before — it’s one of the main fundraisers for the nonprofit, which provides character-building wilderness experiences — but this was my first time participating.

Roller coasters are a favorite, and I’ve leaned out the side of a helicopter dozens of times on photo shoots, so when colleagues asked “Are you nervous?” I truthfully shook my head.

Even getting strapped into the harness that’d be in charge of keeping my body from crashing down, I didn’t break a sweat. Helmet latched, gloves velcro’d, training complete; the elevator ride to the roof was a lighthearted affair.

My heart skipped its first beat when I stepped out onto the 29th floor landing. It tapped at my chest with increasing frequency as I walked to the edge.

We were at 2 Commerce Square, that tower at 20th and Market with the diamond cutouts on top. The balcony had similar cutouts in its railing. One of them, I would be going through.

“Crouch on the edge like a cat,” my gallant handler instructed, “and put both hands on the rope.”

I did as I was told, and as I took my final glance down, the pounding of my heart became so loud I worried I’d miss the instructions.

“Now sit out,” the Outward Bound staffer said.

“Sit…out?” I repeated, more as a stall tactic than anything. He nodded vigorously, so I planted my sneakers on the granite and poked my butt timidly off the ledge.

“Out more, straighten your legs,” came the instruction.

“Straighten…my legs?” I asked again. Another nod, and I locked my knees. My thighs were now perpendicular to the skyscraper, 300 feet above the ground.

“Just go?” I asked, making sure I was still breathing. I shuffled my feet, took a couple of steps back — and that was it. I was off.

Time is a funny thing when you’re dangling hundreds of feet in the air. I could see the cars below me traveling at regular speed, and when I looked at the two other adventurers clambering down above me, they seemed normal. But my own body felt like it was moving in slow motion.

My heart may have continued its adrenaline-fueled race between my ribs, but I was no longer concentrating on its thumping.

So I’m climbing down the side of a building, my brain said to itself, how did I get here?

I mentally zoomed both in and out: I’m a journalist at Billy Penn, which is in Philadelphia, which is in Pennsylvania, which is in the United States, which is on this Earth, which is overtaken by humans, which formed civilizations, which gathered in cities, which got built up by skyscrapers, one of which I’m now hanging off.

I saw with surprising clarity my current place in the world.

Moments of self-realization like this are a stated goal of Outward Bound, which has led challenge expeditions for more than 50 years. Since 1992, the Philadelphia chapter has served more than 6,000 students, and last year opened a new Discovery Center ropes course in Fairmount Park.

The school’s stated mission is “to change lives through challenge and discovery.” When I mentioned my rappelling adventure to a friend, he confirmed that’s what happened to a brother who was in his early 20s. “That place turned his life around,” my friend said. “He was in a dark place — it helped him get excited about living again.”

Studies have shown Outward Bound expeditions can instill leadership values in children and teens, benefit veterans dealing with PTSD, and strengthen teamwork in corporate environments.

Team-building even happens when you’re acting like Spiderman.

There were two other women doing the rappel at the same time as me, and we quickly became a unit. Around the 20th floor, two of us who’d dropped down first decided to wait for the third. The rest of the way down, we kept each other calm with regular shouts of “You ok?” “Yeah, you?”

As my feet touched the ground, all the nervous energy rushed back to the surface. I was sweaty all over, and my legs were shaking so much I could hardly walk. But I felt totally exhilarated.

“I can’t wait till next year,” I told the Outward Bound staff as they helped me unhook. “I’m totally doing this again.”