My mom is dying, how do I cope…

I’m hurting so badly. I’m 25 and very close to my mom. It’s weird because it hasn’t hit until recently that my mom is going to pass away… I don’t know how long she has… she has lung cancer and was doing sort of ok, then it’s like she went way downhill a few weeks ago… she didn’t need an oxygen tank weeks ago and now she does… I think about all the times I got annoyed with her for worrying about me, how I should have visited more often. I did see her once a week most of the time, but I can’t help but think I should’ve made more effort. I know she knows I love her though. I take care of her and help feed her… it’s just so hard to see her like this and it’s no way for a person to live, but I don’t want to let go. I don’t know how to cope and all of this sadness is hitting me late at night.