I'm going to take the time to nominate this for the dumbest post of the year. If you didn't enjoy running, then it's a good thing you quit and if you enjoy your life more now, then more power to you. But to arbitrarily say things like "It's not worth it to continue much past 20..." is beyond dumb. This may shock you, but some people run because they actually like it. They really don't give a damn what it "counts for", which is a joke anyway. What, did God give you Universe Points for having sex with some random girl or lifting weights? Pretty much every activity is pointless when viewed on some grandiose scale.
To the OP, live the life you want to live. If you truly enjoy life more now than you did before, then great, keep doing what you're doing. You'll have to find out what is best for you. Maybe that's training hard again, maybe it's quitting running altogether, or maybe it's something between the two. Just don't listen to clowns that say you can't run and have a social life, date, make money, etc. because you definitely can.