Idiom
let slidelet (someone/something) slide
to not do anything about someone or something.She misbehaved a bit when she got here, and I let her slide because she was in a strange city.It's easy to let exercise slide when you feel bad, but that's when you need it the most.
Usage notes: often used in the form let it slide:
Kids don't like practicing because of the repetition, and some coaches tend to let it slide.