Random Thought

Hello, people! I'll have japanese exam in an hour but i can't resist from writing what i thought just now. 

So, i don't know why but suddenly i started to think about relationship between two people (yes a boy and a girl). I wonder what makes a couple could stay together for a very very long time. They don't even married yet. But why? I know it's such a stupid question, but just wondering. Okay, lets say, me and my bf have been together for almost 4 years. What makes us stick to each other that long? Is it pure because of what-they-call-LOVE? Yeah, no doubt that i love my bf. That's something that doesn't need to be questioned. But is it possible that a couple stay together, not because they love each other but more because they need each other? What i mean by 'need' here is, for example, because you've been together quite long, you've been through a lot of things together, you've done many things together, then those what have happened make you have this 'what will my life be without him/her?' thought/feeling.

And if that's really happening, is it right to keep a relationship like that? Well, for this question, i have a weird feeling actually. Somehow i wanna know the answer, but i feel like i don't wanna know too. 

Hmm..this thing called love and things related to it sometimes are sooo confusing. 

Anyway, wish me luck for the exam ;)