Don't lend things unless you are prepared for them to get damaged, dirty, lost or just not returned. If the item is extraneous consider just giving it. If you don't trust or like the person enough that you would lend them the money for the item if they needed it and not care too much if you got it back then don't lend them the item.
I have lent my best gear to my adult kids with good results although they are not quite as good at cleaning and maintenance as I would like. I figure if it does get lost or broken I'll get to hear about their adventure and getting new gear can be fun.
Sometimes a lent item comes back better. I have a giant family tent I lent to the parents of one of my kids friends and it came back in a new REI duffel!