Two years ago I permanently deleted my Facebook account. It's one of the best decisions I've made as an adult.
It's kind of hard to explain the confluence of factors that led me to delete my account, and even if I could some of the details are more personal than I'd like to share anyway. But the short version is that there was a lot of stuff going on in my life that was causing me to be unhappy. When I would go on Facebook I felt like I was thrust into the middle of a situation that was causing me a lot of anxiety and wasn't making my life any better; in fact, it was making my life worse.
There are certainly a lot of upsides to having a Facebook account. Without question, it makes maintaining social relationships with people that you don't see every day much easier. It's a convenient and easy way to store photos and share photos with friends and family. It also makes it a lot easier to coordinate events and parties, and to get invited to other people's events and parties. It's easy to create accounts on a lot of third-party sites using Facebook login.
However, Facebook also makes a lot of real world social relationships a lot more complicated. The dynamics of the platform encourage you to "friend" people liberally which means that you give a lot of people---many of whom you probably don't know that well---a lot of accesss to information about your life. There are privacy settings that let you control which groups of people can see what content, but then you are forced to artificially group your contacts into a strict set of buckets that doesn't actually mirror how relationships work in the real world. I don't have a strict mental compartmentalization of everyone I know, they all exist in various contexts to me on a gradient that isn't expressed with groups or circles. Even if I did, I don't want the cognitive burden of choosing who should be able to see what for everything I do online.
Facebook makes dating people really weird. To start, there is this stupid binary and public division when you're "in a relationship" with someone or no longer in a relationship with them; a distinction that can lead to unnecessary drama. If you manage to avoid that you invariably end up with a lot of photos, content, etc. linked to past romances. This leads to a weird situation where when you enter into new relationships with other people it's easy for them to learn a lot about your past relationships, and vice versa. That dynamic is part of what leads people to editorialize their profiles and photos after breakups (another recipe for drama). The liking and commenting semantics of Facebook make it a lot easier to speculate about possible romantic relationships and interest than it would be otherwise.
After deleting my Facebook account (and my LinkedIn account), I'm a lot happier about what information people can easily look up about me. I have a public account on Instagram, Twitter, and Tumblr; but I don't post anything that I would consider to be very personal to any of those accounts. If you want to figure out where I work or where I went to school, you can put two and two together if you're diligent; but it's not that forthcoming from any of my public accounts. You can't easily tell who I socialize with in real life from any of these accounts.
It's different for every person, but there have been numerous studies showing that Facebook usage is negatively correlated with happiness. While I'm sure this is not the case with every person, it's something that I experienced and it's easy for me to see why this can be the case. If you like Facebook and feel like it brings value to your life, by all means continue to use it. But if you suspect that it might not be affecting your life in a positive way then I encourage you to reconsider whether it's something you want to have.