Sitting on stand for hours doesn't mean you have to do nothing. Occupy yourself with concentrating on your 'scan pattern'. Back and forth, looking for something out of the ordinary at the extreme limit of what you can make out in the brush (assuming you're hunting in woods). That takes mental effort, which helps pass time. Also, if you're doing it well, you can often avoid that 'deer out of nowhere' phenomenon that they're so good at doing (if you're not paying attention). I find it really rewarding to spot a deer long before they're near my stand location.
As you're scanning, take the time to look for non-deer related stuff that would ordinarily get overlooked. Maybe a songbird doing his thing in the next tree, a squirrel farting around below, a porkie ambling along. That weird tree that grew on top of a rock. Whatever you can find. There's a lot to keep your mind busy if you let it.
Also, I find that switching stand locations every couple of hunts helps because it changes the scenery.