Really? I'm not sure I agree with this in English either, then. To me "treat/reward yourself" suggests performing some sort of specific action (not that this has to be the purchasing of a physical object or something, it could be something as simple as taking one hour out of your busy schedule to read a book that you like or listen to music, or something). "Be kind to yourself", on the other hand, is more about adjusting your state of mind. If I was talking to a friend who was frustrated about their job, or school, or something, and seemed to be blaming him/herself for a bunch of things that weren't really his/her fault, I might say something like this -- or "Go easy on yourself", or "Cut yourself some slack", or the like. I wouldn't say "Give yourself a treat" unless I wanted to suggest that the person actually _do something_ that they wanted to do as sort of a present to him/herself.