Regarding Christmas and the kids, the way I deal with it is that I make it all about my daughter and not about myself. Divorce is tough on the parents, but it is tougher on the kids. So, at Thanksgiving and Christmas, I ask my daughter what she wants to do.
The way we have it set up, my ex gets her Christmas eve and I pick her up Christmas morning and have her the rest of the day and that night. Last year my ex was sick and Lauren didn't get to see her mom, which upset her greatly. So, after we had Christmas dinner with my family, instead of keeping her, I brought her back to her mom so they could spend time together.
The other thing I do is not worry about the quantity of time, but rather the quality of time. Quantity is important, but not as important as quality. Now, I do monitor the quantity of time so that I don't neglect her and start doing things mostly for myself. But, I leave it up to her a lot of times and say, "Hey what do you want to do?" If so choses to do something else, then I go and do something productive for myself.
It can be frustrating at times, but my daughter knows that I put her first, which makes all the difference in the world.
God Bless and Mary Christ-Mass!