Is there really light at the end of the tunnel, or do our eyes just adjust to the darkness?

I’m fairly certain I come from a long line of diagnosed and un-diagnosed mental illness.  My maternal great-grandmother committed suicide when my grandmother was eleven. Unfortunately, I never really took the time to ask my grandmother how it effected her as a child and an adult, and now she’s recently passed.  I have been diagnosed as bipolar by two psychiatrists, but when I returned to one of those doctors recently after a couple years gap, she seems to be rethinking that diagnosis.  I’m not seeing a professional right now because I have a hard time justifying spending $50 to see the therapist every week, plus another $50 one or twice a month to see the psychiatrists, plus whatever the cost of whatever awful zombie-inducing pills are in fashion this month….all so I can still feel like shit; hate myself and most of the world.  I know very well that I have far more reasons to live than to die, but trying to cope with the world and life in general feels almost insurmountable.  I am so angry almost all the time.  The only real ray of light in my life in my three year old daughter, but I don’t know how long she can shine with how shitty I am.  Surely, all the negativity I bring to our lives will turn her as bitter as me?  Her father isn’t necessarily a well balanced individual, but I think she stands a better chance with him than with me. I want to see her grow up, but I’m so terrified I’ll fuck her up.  I know it’s cliche to blame ones parents for mental issues, but my dad has always been such an over-baring prick, I’m so afraid I’m turning into him and she’ll turn into me, and the cycle continues.  If I break away, her father is calm and loving and supportive.  My mom tried to OD on some pills a couple years ago, and I was so mad, not because she tried to take her life, but how the fuck was I supposed to if she did?  She seems alright most days, but she also has a habit of taking on more than she can handle, so most of the family stays in a state of anticipation for the snap. AND I DON’T WANT TO GO THE REST OF MY FUCKING LIFE LIKE THAT!!! I can’t see living every single day, knowing that I won’t ever really be better, that some times I’ll have days not as shitty as others, but for the most part feeling like everything fucking SUCKS.  But what happens to her if I go?