Mindfulness exercises help. So do choosing some projects to concentrate on. As for projects, you'll surely have a good amount in a new job, but pick an easy and enjoyable one for your free time.

Many of us struggle with weight gain, especially around the holidays and during certain mood episodes. There are times I just resolve to work at not gaining more (or much more) in the time being then when the time is a bit better, concentrate on losing. It's possible your new job will occupy you enough for that to happen without major effort. When you get home, if you have a healthier focus to relax or cope, it's best.