Overwhelming depression

I'm a fairly happy person, but I've been severely depressed since 2005, diagnosed in 2012. Most days I'm happy and social and everything works (medication does alot).
Certain things can trigger these extremely overwhelming depressed feelings though, that I just don't want to exist and it's all pointless anyway.
This morning I had a lack of sleep, was already annoyed that I was gonna see my ex again (who apparently takes the same train now even though she lives miles away from the station and does nothing but stare mean the entire time... Childish!) and when I went to sit down it was next to another "ex", someone I almost started a relationship with but we didn't hit it off cause I messed up after I was drunk one night. I'm a former alcoholic, sober for some years now.
Shit like this just seems to turn a button and open the floodgates of depression and shame and melancholia and a sense of doom and pointlessness.
Sport helps, but only temporarily. Mostly I just want the good times back and the pointless times to end. I just don't have any courage of fight left in me.
What do you do with the overwhelming feeling of depression and not wanting to exist anymore?

Abstraction · 61-69, M

Medication numbs it, but it's therapy that gives you the breakthrough. You might need to try a few before you find the right person - but seriously worth it. It is NOT primarily a chemical problem - that too is a symptom.

Cognitive Behaviour Therapy (CBT) is the evidence-based most successful approach.

I had chronic depression 15 years. Haven't been depressed in the last 10 years.

Ludolphus · 31-35, M

@Abstraction I've been going to therapy for the past three years and quit recently and I feel I'm better off without it though. It's like I'm starting to solve my life myself now instead of relying on others.