How do long term relationships work?

DO i really have what it takes to keep this going?

I'm not sure...time and time...i keep feeling like running away..
it's a constant thing...though there's no arguements...
no particular incident that cld cause this...
I just sometimes start to think..mb..just mb...this is enough...
what do i mean? I don't really know..this phrase just pops in my head...
and then i just feel like giving up..selfish-probably!

Pms?is it really?cld it be? it just ended tho..

being apart feels sad...and to some extent feels distant..
when he's sick and not feelin well..i can't be there..
what he's really experiencing..i can't exactly comprehend..
I feel upset that i'm missing him...also upset that i caused him to miss me..
Remind me why we first started...then remind me where we're headed..

why is my heart seemingly wavered? Feelings haven't changed...
just emotions? how do long term relationships work? how do we make it work?
why do we even try to make it work? Is it really worth it? cld it be better to just let the other person go...why keep him next to me while i'm so unstable..
am i really mature enough to handle this? Dad thinks i need to grow up..
will i ever?

sorry for the ranting..just feelin down these 2 days...
feels like i'm procrastinating big time again...been shoppin today instead of studying...just really consciously not feeling like studying...=(