Work Bitterness Still Lives

Even though it's been 6 months since I've officially come over from my old company to the new merged one, I am still bitter about the whole thing - the fact that we were taken over, the fact that I was happy and fine the way things were. I don't find myself completely onboard with this new company, and I'm not motivated to do my job as well as I could. I need to get over my bitterness and move forward as this new company has allowed me to continue my lifestyle without any drastic changes, but my bitterness is still there and I can't make it just go away. I can only acknowledge my feelings at this point and give it more time.