Lending money to friends that don’t pay back (on time)

Three months ago, I started the ‘frugal’ lifestyle, and started saving for the first time. Before that, I used to spend recklessly and often ended up with nothing in my bank account, or even in small debt. Now that I’m saving, I’ve been noticing that my friends take a long time (or don’t pay me back at all) when I cover things like concert tickets or dining out.

I’ve made it clear that I’m serious about saving, but I still have to chase them down for my money, which I don’t like to do. This is all together very stressful for me.

Has anyone been in a similar situation? How did you handle it?