It depends. For me, I don’t have to do that much, I just think to myself “well done. You did it even though you didn’t really want to and because of that you will soon be a better person”. You might watch you favourite tv show or movie, or have your favourite snack, it doesn’t really matter. Just do what makes you feel happy and accomplished.
Usually I try to find an activity that I really enjoy to do, like going to a drive-in movie or cooking my favourite dinner that night. I prefer activities that I can do with a friend or with my husband, so that I can reward myself with a good time instead of something material.