I DIDN'T REALIZE I was scared until I realized how slippery my hands were. And once I realized how slippery my hands were, I realized I was probably going to die.

Just to be clear: When this happened, I was most of the way up a 40-foot-high wall, and the only things keeping me from falling were (1) a rope around my gut, and (2) my sweat-slicked hands.

I've always wanted to rock climb. I've also always been terrified of heights. That looks awesome, I'd think, whenever I drove past the Portland Rock Gym or saw a few seconds of Sylvester Stallone's Cliffhanger. But no fucking way. I would lose... my... shit.

Turns out I didn't lose my shit—but I got pretty close.

The Portland Rock Gym's intro class is a three-hour affair, with the first half spent on the ground, focusing on how to put on the harness that fits snugly around your waist and thighs, how to "tie in" to the ropes that lead to the top of some of the gym's four-story walls, and how to "belay"—use that same rope and harness, along with a carabiner and a lo-fi "air traffic controller" (ATC) device, to safely lower climbers. The second half of the class is spent climbing: After splitting us into pairs, our expert instructor Nora turned us loose on one of the faux-rock walls. With one person climbing and the other on belay, we started clambering up sloping angles before tackling harder routes.

Climbing and belaying are challenging in different ways: When you're on belay—on the ground, controlling the rope that's tied to your harness, looped through a hook at the top of the wall, and onto the climber's harness—you feel like you've got another person's life in your hands. A lot of the work is done by the ATC, which slows down the rope, meaning the climber can't fall too fast. (Nora aptly described the ATC as a "friction machine.") But the ATC requires skill to use—here's where you put your left arm, here's where you keep your right, here's how you gauge tension in the line—hence the instruction before using it, and the fact that anyone using the Portland Rock Gym must first pass a belay test.

Climbing was, somehow, both easier and harder than belaying. I knew I'd only be able to climb if I dealt with my fear of heights the same way I deal with my fears of student loan debt and emotional commitment: blithely ignoring it! Instead, I focused on putting one hand in front of the other, pushing with my legs, and quickly ascending. I got this, I thought, climbing with surprising speed (and, if I say so myself, a rather impressive amount of grace). This is great! And it was: seeing how quickly and ably I was able to scale a near-vertical plane was fun, and I felt good doing it; Nora was a clear, effective teacher; my belay partner seemed moderately confident that she wasn't going to let me die, and for the first 20 or so feet, I had no problems following the color-coded route up the wall.

Somewhere around foot 30, though, the handholds got harder to spot, farther apart, and increasingly smaller. It was a spot where, in order to find a handhold, I had to stop, take a breath, and plan my next move. Naturally, it was also a spot where it became impossible to forget how high up I was.

At which point I noticed how sweaty my palms were. I might be able to trick my brain, but apparently I can't fool my sweat glands.

"Ready to lower!" I called down—and while Nora shouted up a few encouraging tips, calling out handholds that I was too chickenshit to reach for, I eventually settled my weight into the harness, pushed off, and came down. I wiped the sweat off my palms and looked up at that goddamn wall.

Next time.

Portland Rock Gym, 21 NE 12th, intro class Sat-Sun 9 am and Wed 7 pm, $52, includes one-week membership and equipment rental