Good suggestions here. I have a few more. Bring a couple of those handheld, electronic card games, checkers, yatzee, whatever. Turn the sound off. Bring your camera, and take pictures of birds and whatever wildlife you see. Make it a goal to get a picture of certain birds, that will give your mind something to do. Relax. Think about life, the things that bring you down, and overcome them. Think about things you have done good in the past, and things you have done bad in the past. Make peace with the Lord if you need to. Tree stand time is a GREAT time of reflection. Don't forget to bring some good snacks, like deer sausage, nutty bars and apples. That is an awesome combination, seriously. Don't forget some water, too.

Here's the thing though. If you can't do it, don't. This is suppose to be fun. If you just keep forcing yourself, you will resent it, and eventually will become a burden and you won't want to do it anymore.