Every girl has three guys in her life. The one she loves, the one she haters and the one she can't live without. And in the end, they're all the same guy.
Trying to understand love is like trying to understand life as we know it, and is something that we will probably never truly all the way understand. What I have learned from my own personal relationships and from my elders who have been married or with the same person for at least ten years is that even though you may love your significant other, there are going to be differences in opinion, and arguments sometimes, there are going to be places you want to go that they might not want to and vice-versa, but at the end of the day there should be no one else you would rather be in bed with than your significant other.