Bad habit

I have a bad habit of loaning money to friends. You'd think because I've had so many people that have never payed me back that I would learn a lesson from it but if a friend needs something I usually do whatever I can to help. Recently my best friends boyfriend asked me to get a necklace for him to give to my friend for valentines day. I absolutely trust him to pay me back but what always happens is they put it off for so long and eventually forget, hoping that I will forget too. And usually I do and when I finally remember it's been so long that I feel bad bringing it up.