When is resting become a weakness?

so this is a question to people that work out a lot, so we all know that every once in a while (every 2 or 3 months) we should rest our whole bodies for a while like a week or 10 days but when does the rest start making you weaker for example when I went on vacation I didn't work out for 3 or 4 weeks and when I came back I was so weak I was benching 50 less curling 30 less etc so when does rest start making you weaker instead of recovery
When is resting become a weakness?
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