On one hand, I once deleted mine and didn't regret it. It felt like a relief to not have to worry about that aspect of my life. It wasn't until I re-made it that I regretted deleting it before (and I re-made it because I almost feel like I have to have one in my situation) because I would've had more friends than I do now.
On the other hand, I agree with johnkim that keeping it could be better. Even though it causes you stress, it might help you grow stronger if you keep pushing yourself mentally in a positive way. I struggle with my Facebook too but I try to stay positive since I can't delete it now. I have very few friends and it's embarrassing for new friends to add me and see that. But sometimes people think so differently that they might barely think anything of our friend count. Some might just think that we're not the type to add everyone or it's a new account, etc. There are also those who look down on those with 500+ friends.