ADHD-related anger?

hello everyone :)

Let me start out by saying I'm so glad I found this site!!! I can relate to so many ADHDers on here! Now on to my point.  My boyfriend and I have been together for a little over three and a half years.  Over the years, we have come to the realization of how much of an angry person I am/can be. He thinks of me as "unhappy" person and now, I do as well. Up until recently, I thought it could be due to the depression that runs on my mother's side of the family. My grandmother is a VERY unhappy person. Constant negativity and constant nastiness to other people. Possible contributing factor?  Possibly. But I'm not nasty towards other people. And for the negativity? Lets just say I could look on the brighter side of things a little more often. What has led us to this conclusion, is I explode over the littlest things A LOT. Not as much as I use too, but I still do it. He has told me in the past that he only likes being around when the happy me is present. Also, I have a hard time with letting the little things go and overreacting. I know this in my heart. If I don't get my act together, its splitsville for us (he has also told me this multiple times). We've been trying to work together on improving our relationship for a couple of years now. With some improvement, but not complete satisfaction. I'm delighted I came upon this website. I'm hoping it'll help me with my ADHD related issues, and therefore, improving our relationship. We have discussed splitting up, but we both agreed that we don't want too give up on one another yet, if ever. But sometimes I wonder if we're beating a dead horse. How do you know its time to throw in the rag? When do you know that time has arrived? I love this man dearly, and I would be devastated if I ever lost him. I'm a very lucky woman to have him in my life. Especially after 3.5 years of at times, hell. I am at a loss as to what to do. Any tips or advice would be greatly appreciated!! Heck, even someone responding that can relate to my situation would be uplifting! :-D