I'm certainly not the leading expert on relationships but after being married for 9 years and now divorced, I think I have a few relevant things to say. A lot of people like to ask "what is the one piece of advice you would give to someone about to xyz". I'm always a bit reluctant to answer because there are so many things to be said that attempting to choose one tip is a bit daunting. That all being aside, I'm going to attempt to do just that right here, right now.
Most people in the world are insecure to one degree or another. Insecurity in a relationship is the mechanical equivalent of constantly checking to make sure a screw is tight and in the process stripping it out. Fear is the mother of insecurity and obsession is her grandchild. In that family every little thing is weighed, analyzed and a belief formed around it. Having to constantly prove you love someone is exhausting.
You don't however, have to be intensely insecure to be able to take note of my one relationship tip. Even "normal" people make wild assumptions off of passing data and while I may not rock them to their xore, it can still create problems.
People are different and many of their actions are certified gray area. What the hell am I talking about? When you get into a relationship you are trying to merge your set of life experiences (hurts, joys, familial culture etc) with theirs. Every one lives life anywhere from a slightly divergent outlook to an almost 180° approach to you. Your partner may do something that to them is insignificant but the only explanation in your mind is "they must not care about me that much". I know how the mental battle goes because I've been on both sides of it. While the thought "if they love me, they would make an effort to do xyz" holds some weight, are you really wanting to make them just like you? That's called control and only fearful people and assholes are controlling. Now to be clear, I'm talking things like "he forgot to get the milk I asked for" or "why isn't she responding to every text" type things. Not "I wish he wouldn't cheat on me" type situations. The beauty of the world is that everyone is different and the sooner you open up your heart and embrace that fact, the sooner you will find peace.
Find someone you not only love but really like as well. Then love them always and always trust in their love. When the thought comes "I know they love me but..." cut it off there, accept that love and embrace the quirkiness because baby - we're all quirky.