I don't have a lot of advice on how to make a relationship work, but I have a lot of advice on how to destroy them, as I'm pretty experienced in that regard. Firstly, you're never going to be excited to be around one person all the time. The problem is that doesn't meet everyone's fantasy and they jump ship. It's easier than sticking it out. That's bullshit. Are you excited to see your family all the time? Probably not, but you love them in a way that's well beyond infatuation.

Second, if your partner isn't meeting your expectations about some issue, bring it up to them. It's shitty to have to have talks like that but it cleans the wound. Otherwise, you'll end up with the relationship equivalent of a trench boil, and it will puss all over you. Been there. Not fun.

Lastly, if you really think of someone as a long term partner, think about what that means to you. Practical things aren't sexy at all (what are my career goals? do I want children? etc), but it's a lot easier to sort that shit out earlier rather than waiting a few years to find out that you aren't on the same page.