Loneliness as trigger. Gotcha.
Be around people. Write in cafés. Regardless of therapy that's fun in itself.
The real killer is disappointment followed by loneliness. Where something planned falls through, there's a last-minute cancellation, or you're stood up. Then you're alone and all dressed up, usually figuratively, meaning the movie in your head has gone dark, you're hurt and confused, you feel unimportant, there's anger, you have no outlet for any of this, you'd like to be asleep or high or both in whatever proportion would make these feelings go away.
The logical solution would be to cultivate many many many friends, so that when something or someone you looked forward to bails, there are potential alternatives. But, you've never had large numbers of close friends at once, and people your own age have kids to take care of, and people younger are already taken for the evening. So that you spend a dark time alone at home with your metaphorical finger up your nose trying to pull out something worthwhile. Maybe a song, maybe some vignettes. Until exhaustion and sleep lead to blissful oblivion, or, better, dreams of the naked flesh that should be sleeping next to you.