Don't choose someone based on their damage
We feel compassion.
And in a moment of great trial for one or both, bonds can be formed.
The thing is that personal pain is terrible soil for a relationship go grow in. It doesn't produce health. It drains.
This can be in romantic relationships, friendships and even family.
I don't believe it is bad for a relationship to start with a connection over shared pain, but it absolutely cannot stay there. Pain has to be walked through and experienced so it can do it's work, but it can never, ever be the destination. Love has to be the destination. Love is generative. Love brings joy, healing, forgiveness, light... Love has energy to it and moves forward. You can usually tell its absence when things are standing still.
If you find that you have relationships where you felt you could heal somebody's damage and are now feeling exhausted by it, then it is probably time to re-evaluate.
The thing about love is that it must be received and embraced. Sometimes people choose pain over love.
And you can let that be their choice. It doesn't have to be yours.