Learnt this one early.

My first serious gf was manic depressive. Stood by her through thick and thin. Took her to the hospital and stayed with her for days when she tried to kill herself. Stood by her side while she told her family what was going on with her. Supported her while she didn't work and took some time to sort through her issues. Encouraged her to seek therapy... even attended a couple of sessions with her.

As soon as she started feeling better she said she needed space.

"Space" meant drinking, smoking weed and fucking the guy 4 doors down who had a motorcycle. Every morning i pulled out my driveway and saw her car out the front of his. Every night when i returned home they'd be on his porch. It was torture. Of all the streets in this city... why mine?