He/she is a projection of your idealized version of the person you like.
What happens when he/she does something different from how you’d imagined? You’ll either feel hurt that he/she isn’t doing what you want “anymore”, and perhaps try to change that person (which will not be well received).
So, to start off, try to not imagine what it’d be like, or how good it would be.
This is where an intuitive mind trying to analyze tons of possibilities becomes extremely harmful. The other thing that happens when you think about your future together too much is that you are analyzing too deeply down one branch of the possibility tree.
Knowing what you’d do in this situation really helps you out in figuring out what you want.
You have to learn to like yourself in this state because then, any kind of relationship breakup wouldn’t be so bad.
Aren’t those situations of you being alone completely unlikely though? In fact, outside of very involved relationships, you are alone most of the time.
It’s also when the other person feel this exceeding neediness from you, which leads the the suspicion that you have much less to offer than what you’ll be getting.
There are just so many things that can change that particular possibility. All your planning has been focused on the two of you being together, so when the unexpected happens, you have no alternate plan! Say there were no people in the world, what would you do?
This is when people sit at home crying, blaming the other person for not fulfilling their dreams. Now say there were 2 people in the world, what would you do?
Did you just go out on a date and wonder how it went?
Are you staying up all night wondering if he/she feels the same way you do? Pretty much everyone has been in this situation at one time or another.