С-11

HE В СВОЙ САНИ HE САДИСЬ (saying other finite forms and infin are also used) do not undertake sth. that is more than you can manage: - don't bite off more than you can chew don't try to do something (things) you're not fit for.

(author's usage) «Я вижу, образование у неё небольшое». -«Какое там образование - грамотёшка! С таким образованием только получку считать, а не казённые деньги. Я ей сколько раз говорил: не лезь не в свои сани. Работать как раз некому было, ее и уговорили» (Распутин 1). uShe doesn't seem to have had much of an education." "Education? You're joking. Can't do much more than count her pay, let alone the till. How many times did I tell her: don't try to do something you're not fit for. But there was nobody else to take the job and they talked her into it" (1a).