An idiom meaning the blame, harm, or punishment one receives as a result of one's own actions; similar to 'you reap what you sow' or 'paying for one's mistakes.'
彼は不正を働いて解雇された。身から出た錆だ。
He was fired for committing fraud. It's his own doing.
約束を守らなかった結果、信用を失ったのは身から出た錆だ。
As a consequence of not keeping promises, he lost trust — serving him right.
投資の失敗は勉強不足が原因だ。身から出た錆だと思う。
The investment loss was due to lack of knowledge. I think it's my own fault.