stick to your last
stick to your lastBRITISH, OLD-FASHIONED
If you say that someone should stick to their last, you mean that they should continue doing what they are experienced at and not try to do new things. Looking back, I should have stuck to my last and gone on to get a research job in one of the studios. Note: People sometimes use the whole phrase let the cobbler stick to his last, or change part of it to fit a particular situation. You see before you an embarrassed cobbler who will stick to his last from now on. I was afraid they'd think, `Why can't the cobbler stick to his last?' Note: A cobbler is a shoe maker and a last is a foot-shaped object used as a model to make shoes the right shape and size.
stick to your lastconfine your activities to the area you have personal knowledge of or skill in.
The expression derives from the proverb ‘The cobbler should stick to his last’, a last being a shoemaker's model for shaping or repairing a shoe.