Loaning money

So this guy who I work with his grandma lost his keys and he has to pay 170 to get a key made, well he doesn’t have money because he barely works due to scheduling issues (managers fault, got it fixed now) and paying bills and trying to get an apartment.. well he and I had a past, we ended up having drunk sex about two months ago and we talked before it happened and were really close for a few weeks and then the sex happened and we fell off and never worked together and now the past couple days he’s popped back into my life and we’re sorta talking and what not. Well we were having a conversation and the key came into it and I needed up loaning him $100.. his schedule is full with shifts now so I know I will get the money back soon and he told me he would, but how big of a mistake did I just make? 😂 I’ve never loaned anyone money before so I feel crazy for doing it but I just felt like I was suppose to