Why do we do it?

As I’m reading through a lot of posts and thinking about everything I have personally been through in my last few relationships, I’m left with one question I can’t seem to be able to answer so I’m hoping you wonderful people can help me maybe shed some light on this.

Why do we put ourselves through so much pain and anxiety? Why do we stay? Is all this pain really worth it? Why do we lose ourselves for people that hurt us and will keep hurting us? I guess what I’m really asking is what’s the point? What’s in it for us? If you found out you had only a couple of years to live, would you still accept all the behaviours and lies and disrespect? And if your answer is no, than why do you accept it now?