Herbie, I had to reply to your post and give you a cyber (((hug)))
My eldest daughter is bipolar and we have been through very similar times with her, the awful thing about it is when they are manic they dont want to take their meds because they feel so fantastic, and then of course they come crashing down - sometimes with devastating consequences. All I can say is that my daughter learned from her mistakes (admittedly slowly) and she is now studying Law at Manchester and keeping herself fairly level.
The most important thing you can do for them when they are on a down cycle is listen - my daughter feels totally worthless when she is down - tell her how much you love her and that you will always be there for her, but also that she has to learn from the whole cause and effect lesson. I check on a constant basis that my daughter is taking her meds, and also make sure that she is reminded of the consequences if she doesnt, not in a nasty way, Just a gentle nudge or an almost joke, but so she knows that I am involved and behind her/ keeping an eye her.
I hope that she feels better soon, don't ever feel guilty herbie , you cant make her better, you can just try to help her to heal herself.