living together

me and my boyfriend have been together for over a year and we both moved out of state and into an apartment together for the last 3 months. he decided we should get our own apartments once this lease is up, and it freaked me out a bit. i've calmed down a little bit about it, he says it's to gain maturity and know how to be on our own. but a part of me can't help but think "why, is it because you'll end up leaving me?" and i start to overthink the whole scenerio. does anybody have any thoughts on this that could make me feel better, or at least any opinions?