There are a lot of people who abuse the kindness or generosity of others. I just avoid them if I can. Thankfully none of my close friends are like that. I don't think I could get along with a person like that anyway.
I have an office mate that had a habit of bumming cigarettes from me. Then I noticed that he barely buys his own anymore! He also borrows my lighter and always "forget" to return it. It's so frustrating when you need a smoke and not have a lighter. Since he's a heavy smoker I need to replace my lighter more often that usual

I just stopped smoking because I didn't want him to abuse me anymore. BTW, he already had a gap with another office mate because of that habit. Now he does not have a smoking buddy anymore. It seems like the smokers in the office are avoiding him already
Another example, I have a cabinet in the office that I stock up with chips, crackers, nuts and chocolates. My friends at work know that they can get food from there any time. I get pissed when I buy a whole pack of something and I never even have the chance to try it kasi nauubos agad. Hindi man lang ako tinirhan

I don't make a big deal about it anymore. I just take note of the food that are "popular" and don't buy it anymore next time
I also have office mates na napakalakas mag kantyaw sa libre pero pag sila ang kukunat. Minsan pag talagang naiisip ko naabuso na ko iniisip ko na lang sinasabi ng mga magulang ko na maswerte ako I have enough to share.