He was chosen for the mission in a large part for his lack of emotions: stress didn't seem to phase him when in precarious situations.
Buzz Aldrin was a bit more emotional in comparison, but still a rather mellow person. Buzz was chosen for his MacGyver-like abilities to improvise. He did end up dissecting a ball-point pen to trigger a damaged switch. A fully-inflated space suit ended up bigger than drafted, and they had a hard time getting out of the hatch, brushing up against instrument panels in the process. Good thing they didn't bump the "launch" button :-)
Perhaps in contrast, First Man (the book) relates that Armstrong hid in a college bathroom when some autograph seekers came by the college where he taught.