Do you know what is causing you to be grumpy and bad-tempered? If so, simply address it and move on. I realize it's not always that simple but if you know the cause you're halfway there.

For the past few months I was angry about my living situation in my own house (I posted on another thread so I won't regurgitate here). I finally snapped and instead of playing Mr. Nice Guy, I finally stood up for myself and told the cause of my angst that enough in enough and that she's not going to call the shots anymore. She of course didn't like it and we had WWIII over the phone and, yes, it was uncomfortable but SOOOOOO worth it. I got my house back and therefore my sanity back. Now sister-in-law is "threatening" to stay out of my life forever. Good Lord, I hope she follows through with it. I am typically a pretty laid-back person but even I have a breaking point.

What I hope you take away from this is life is too short. Address the people / things that are making you mad, angry, grump, etc. etc. etc. and live your best life.