Relationship / not relationship advice :

OK so I have been with my boyfriend for four years and he has been acting very childish lately doing things to make me kind of act crazy , crazy as in like questioning him about his phone ECT.... Hes admitting to it so now that I know that he’s doing it on purpose I try not to react But some days I just don’t know how to ignore it what are some tips that you done to ignore either or your partner or your ex about things that you know they do purposely?