Pick/choose your moment - Idioms by The Free Dictionary
pick/choose your moment
pick (one's) moment
To thoughtfully and prudently decide the best moment to act. Sometimes used ironically to suggest the opposite. I suggest picking your moment before you ask the boss for a raise. Wow, she broke up with him on his birthday? She really knows how to pick her moment.
pick/choose your ˈmoment carefully choose the right time to do something: I wanted to make sure she agreed, so I picked my moment, when she was in a good mood. ♢ (ironic) You told her you wanted a divorce two days after her operation! You really picked your moment, didn’t you?