If you can’t lend it without resenting it, don’t lend it. That’s honest with both of you.

A grudging yes costs more than a clear no. You hand the thing over, then watch how it is treated, keep a private tally, and the friendship takes damage over an item you did not really want to give. The other person never agreed to that version, because you told them it was fine. Saying no protects something more valuable than whatever they were borrowing.

Before you lend anything this week, ask how you will feel if it comes back late or marked. If the answer is bad, say you would rather not. You can offer something else instead, but do not offer the thing you will be counting.