How to handle intermittent but prolonged mourning

I go in and out of deep mourning for the loss of my marriage.  I'm not divorced; my husband is not dead; but the combination of ADHD, depression, and perhaps a personality disorder have affected him so much that I believe that our relationship is not one of mutually supportive partners and that it never will be.   I realize that it would probably help if we were divorced, but right now, that is not yet a possibility.  Is there any chance that I can move out of mourning on a permanent basis or is it just human nature that I will periodically feel anger and sadness about the loss of my marriage?  Any tips for getting through the sadness in the moment?  Thank you.