Is masturbating once a day too much? i wanna quit it for a few months... i wanna build up back my stamina.

Unlikely a problem: no, that is not too much.

Myth: Sex, whether you are alone or with a partner has little to nothing to do with stamina. Some pro athletes abstain for a while before their games in hopes it would help while others fine sex before games relaxing. You can get involved in self sex bad enough that you may not be able to perform in a partner situation since it differs but that is rare.