There are two doors into friendship.
One is an intense emotional experience. You both watch an accident happen. You both laugh so hard neither of you can breathe. Moments like that fuse people together fast — adrenaline included.
The other is continuity. You see the same people over and over — same gym, same coffee shop, same commute — until familiarity turns into something warmer.
Two doors — most friendships only ever get one of them open
This is why run clubs work so well for making real connections. You get both doors at once. The run itself is adrenaline — shared effort, shared discomfort, shared finish line. And you see the same faces every week, so continuity opens right behind it. Running as a team fuses the two mechanisms most friendships only get one of.
So find those opportunities on purpose. Join the thing that repeats. Look for the moment that spikes. Do both if you can — that's the run club effect, and it works well past running.