Friend who owes you money

Do you usually lend money to friends or try to stay out of this? Some of them pay off their debts, but others pretend like nothing happened and this can really ruin a friendship. So, does any friend owe you money?
Stay out of this. I have lent money to friends before and they pretend like nothing happened and end up not paying of their debts and giving the cash back which in return ruins the trust in the friendship. I'll never lend cash to a friend again, because of this