How does one deal with the fear of a partner cheating?

So, i'm 20, been in a relationship for a year. Obviously i'm not jumping the gun and saying that i'm going to marry this girl, and it's about her in particular. This is just a general question for any relationship, be it with this girl, or a girlfriend after her or whatever.

It seems that everyone cheats. I know not everyone, but i feel like the statistics show that the probability of your SO cheating is pretty high. I just have trust issues. I've had them my entire life. I was wondering, how does one get over this stat and settle down with someone for the rest of his/her life? I just get too paranoid thinking about how many people cheat. It's not even physical cheating that gets me, it's the emotional aspect of it. If my girlfriend was to have an emotional affair with someone then i would find that just as detrimental. I just hate the idea of her trying to make up her mind, while i'm strung along for the ride oblivious to the situation. What's worse is when i hear of someone cheating and how their partner had no idea. Completely oblivious. This is my greatest fear. It's not that i have anything against my girlfriend, it's with girls in general. I just can't bring myself to put so much trust into someone.

Also, sidenote. I know it's all relative, but if your partner were to cheat what do you think would become of the relationship? I know it's all circumstantial but where do you draw the line?

TL;DR: How do you deal with the fear of your SO cheating not just physically, but emotionally. What would you do if you found out that they had cheated?

EDIT: Let me clarify, it's mostly the fear of dealing with emotional cheating. And i'm saying girls in general because i'm a guy...i'm aware it goes both ways.