Those are the types of "loans" that require a two-tiered memory, lol. On one hand you want to forget about the money and try to preserve the relationship. This is especially crucial with family members whom you're likely to encounter regularly. On the other hand, you want to remember to never give them another loan. Usually the second part takes care of itself; if they have any self respect they are unlikely to ever ask again due to embarrassment.
This doesn't always work. So the "if" justified here. Once he got a $20 loan from me, he knew I wouldn't ask for it if he didn't return because the relationship between us was too good. He used to chill together at the riverside and have snacks. Everything was fine even after one year of taking the first loan. Things changed once he got the 2nd loan from me, saying he would return it all together in the next few days.
He stopped picking my phone calls. So I text him a line that $50 worth of money is too small to ruin a relation. He never replied to that. He actually paid a $30 a few weeks ago and he still owe me that $20. I know what is he going through. So, I don't bother him.