When an Overly Hopeful Romantic Becomes Clingy and Pushy

I've been spending a whole lot of days contemplating  my current relationship. The person I've been with for the last 8 months is convinced that we'll be together forever and frequently wants me to promise him that I'll stay. Unfortunately for him, I don't believe the future will be set in stone just because we decide to make a promise. Maybe we will be together forever and that would be great but maybe we can't. The problem I've been having is that if for any reason, we can't stay together, I'm going to feel guilty about it not working out. Since he believes so strongly that we belong together, if we did have to part ways he would likely be incapable of moving on and I'd blame myself for not being able to make him happy. Being happy with him right now is enough for me. I don't need to know where it's going to go. We're only 8 months in and I think it's pointless to obsess over our future together. I almost feel as though I can't make him happy now unless I promise to have a future with him and I don't think that's right. In my mind the most we can promise each other is that we want to be together forever. If you're reading this, I want you to know that I swear to you that I want us to live happily ever after and I hope that can be enough for you.