Another option that I found somewhere as a technique is to add circles for what you have/get, and fill/cross circles when you loose them. E.g. starting with
Health: ○○○○○
When getting 2 harm, fill/cross 2:
Health: ●●○○○
When healing 1, add 1 circle again:
Health: ●●○○○○
etc. (Circles could be included in a template in very light gray, to be outlined when you get them.)