If you knew that your bank was giving earning you 10 percent interest on your saving but was going to go bankrupt in two weeks, would you leave your money in that bank?
I'd pull my money out faster than Usain Bolt running a 10-yard dash.
While it's not a perfect analogy, I have to wonder why you'd stick around in a relationship that you knew was going nowhere? You owe it to yourself and to the guy you're dating to be honest and be like, look, this isn't going to lead any where further than its gone thus far, I don't think you're the guy I see myself with forever and we've had three great years together. Let's cut our losses and go find somebody to make us happy. It might hurt like hell now but it will hurt way less than when he proposes and you're like, "no, and I think we need to just break up and go our separate ways."
People spend a lot of time in relationships trying to determine if the person they're with is somebody they can see forever with. You've already made that determination. Cut your losses. Go out with a bang.
A literal one and a figurative one. But let him know that it's not him, it's you. You just know yourself and realize what you want and perhaps he doesn't fit that and it's not fair for either one of you to put forth effort for something that you're not feeling anymore.
It was written.