would you give me some suggestion?

i have lots of friends who are like that. it's easy for them to just borrow from me but they seem to forget that they do owe me. i feel really upset when friends treat me like their bank account and that they can just withdraw anytime without even depositing! sometimes, if i can't really get my payment back, i really find time to talk to them. if still they wont' pay me, i give them extra time to do so. and find another time to talk to them. some do pay and some are really hard headed.