Not because you are admiring your body (LOL), but to look for areas to improve.
My brother and I since we first started competing have always filmed our performances. It is the easiest way to spot mistakes, learn new moves, and develop improved tactics.
This practice is pretty common amongst serious competitors, but it doesn’t have to be used only for competition – you can do the same for your training.
The way you train is the way you will fight – so why rely on competitions that you do once in a while when you can monitor your daily performances? While filming yourself every day would take time, at least once a week during a sparring session would allow you to learn much faster from your performances.
Reviewing video will reveal mistakes you are making and opportunities that you have been missing out on. You may think you are doing something right in your mind, but the video doesn’t lie 🙂
You may argue that your instructor is supposed to be giving you the oversight, but he or she can only devote so much time to you. With the video, you can study a sequence over and over until you have gained all the insight possible from it.
Nowadays, this is easy to do. Any smart phone can be used to film yourself in action. All you need is a volunteer to film you for 15-30 minutes once a week.