If they want to borrow something from me, they must really be in sad shape. At least, for the moment, I have a roof over my head.
Relatives and friends will take advantage of you when that's your sole weakness. When they borrow money, they'll just have to show you that they are in a sad and terrible shape for your heart to get touched by their emotion and you'll be caught by that as well. With that emotion, it's what you feel about them and even if they have a different reason as long as they're able to successfully touched your heart then you'll later on going to give it to them which is a bad trait. Because I've been there and they'll take advantage of you every time they are in need of money and worse if they don't even pay on due or never paid. 
Lending is a business to someone credit companies most especially in African countries so, the idea of lending what you can afford to forget is a wrong notion.
Try to ensure that every borrower should provide an equivalent property as a collateral. If it is not for profit making then stop borrowing them.
If this is just a person to person lending, and it's mostly discussed about verbal agreements. The requirements will be easy because you're lending them out of good will and your concern to them. But many of these borrowers are going to take advantage of you so, when you get to that point, always point them out with the actual lending business and see if they'll be able to ask money from them easily just as how you as a person lent them.Try to ensure that every borrower should provide an equivalent property as a collateral. If it is not for profit making then stop borrowing them.