Math.
Giving birth!!π‘π€¬π
In the words of Kylie Jenner, 'realizing stuff'. Lol but in complete seriousness. Slowly coming into certain painful realizations as you get older, those are the biggest obstacles I've had to conquer.
Alienation. Message boards can increase probabilities of finding people who love similar things, in my case, music, movies, and comedy.
That's a big one, I agree. Alienation and isolation, those are pretty tough.