People who borrow your money, take forever to pay you back, and then short-change you.?

I've had so many experiences with friends and affiliates who borrowed money from me, then carry on for weeks or even months without mentioning anything again until I remind them. I'm not being stingy but almost everyone of them, when they finally do pay me back, say 'sorry I'm a little short of the full amount, I hope this will do'. What do you think?