I do try to practice/reflect on karma (believe in seems to be the wrong word for me), but more in a Buddhist sense than the Western 'what goes around, comes around'.
For me, I try to be mindful that the only karma I should be interested in is my own, and that it is none of my business to make judgements about whether other people deserve to have good or bad things happen to them.
I try to be mindful to show compassion to other people, even if they have not done the same to me. That doesn't mean that I am a doormat who lets people walk all over me, because of course the first person I owe compassion to is myself.
The aim is to work towards a state of mind that will accept misfortune and good fortune equally. If I am less upset about bad things happening, then I will not have as many bad things happen. Not because they will magically stop happening, but I will see them as less bad.
On the other hand, if I get upset and angry at every bad thing, then I will become increasingly upset as the bag things will gain an overwhelming importance. Likewise, if I revel in good fortune, feeling that I 'deserve' it, I will feel unhappy when I am no longer blessed with it.
I know that Buddhist karma also deals with events catching up with you in future lives, and am a bit more on the fence about whether I believe in that, except maybe to the extent that if one is reincarnated, then the lessons and wisdom you acquire in one life may follow you to the next.
That is my understanding of karma. I struggle to get it right most of the time but it is what I try to work towards.