I used to catch and rip the armholes of sleeveless garments on the lever handles of old-fashioned doors on a regular basis (one of the drawbacks of being short enough for your armpits to line up with high-level handles).
Not so much of a problem now that I have low-level knobs, but it turns out that my forearm is on a level with the sharp edge of the latch, and it's a lot sharper than you realise until you snag yourself on it in passing. Not that the fabric would have ripped if it hadn't been rotten to start off with... unfortunatly it has now got to go back into the wash in order to make clean rag, which means I need to remember *not* to put it back in the wardrobe when it next comes out!

(I have the same problem with holes in socks; either you darn them sweaty, or you have to remember to mend them after washing them, which I tend to forget to do. Then you pull a pair of socks out of the drawer in a hurry and discover that your big toe is sticking out. On the whole the only practical thing to do is to darn them while you are still wearing them -- sadly that approach really isn't practical for holes in pants!)