The scratch on something borrowed carries an awkwardness the same scratch on yours would not.

Damage to your own things is a fact; damage to someone else’s is a conversation. The mark is identical and everything around it changes, since you must decide when to mention it, how much to offer, and whether they will believe it was already there. That weight comes from the relationship rather than the object. Most people dread the telling far more than the cost.

If you have marked something borrowed, say so early, plainly, and offer to put it right. Early is what makes it a mishap rather than a discovery. When it happens to something of yours, remember how easy you can make that sentence for them.