<human>: Can you give me the gist of the text in a nutshell?

I've been dating my SO for 2 years now, and I can't seem to wrap my mind around breaking up with him. I love him, very much so. We've been friends for 5 years, dating for 2, he is my best friend. The marriage conversation has come up more recently lately - and I'm terrified. My SO is all about the conventional family structure, and from the looks of it, sees us together til death do us part. 

However, I know a break up would completely destroy him. I care for him so deeply and I know that it will eventually come to end, but I can't bring myself to do it. Thats not to say the breakup wouldn't destroy me either - I just know this is not what I want for the long term. I'm so young!

Help reddit...how do I approach this?
<bot>: Love my boyfriend, but I do not see us in the long term and guilt is crippling my ability to end it. Help!