Will we Expire?

I know we all expire eventually, in death. But that's not the kind of expiration date I'm talking about. I'm wondering if and when relationships expire? Friendships and your time with your significant other. Those kinds of relationships. After spending what I thought was a good time with certain people, I'm sometimes left wondering if we'll expire. Will it end up being that I'm not that fun anymore? Will they lose interest? Will they just drift away and I'm left alone wondering what went wrong? Could I prevent such things from happening? Sometimes I feel as though I'm not that fun. Like they could have more fun without me. I'm always told that friends and boyfriends come and go. I understand that. 

Sometimes I feel as though taking a breath of air is just a waste of time. But I find myself craving the fresh air that fill my lungs. I crave and rebel against that urge to give up. I keep going, it must mean something. I'm not even sure why I'm writing this. But sometimes, like today, I feel as though there are better things than being with me. I'm not sure. I know it's not all about me, I'm not trying to sound selfish or anything. I'm just wondering if I can get over that paranoia of not being wanted anymore.