I've been dating my boyfriend for 3 years now, and I've learned a great deal from our relationship. One of the biggest things is that the person you date is/should be your best friend. My boyfriend began as one of my best friends and that is what helped build our relationship to be what it is now. If he hadn't been one of my best friends, then I doubt we would have gotten to know each other as well as we have and I doubt we would've remained together as long as we have.
Back in middle school, we went on a date without really knowing each other too well, and it was an extremely awkward hour. Since we didn't know each other well, we spent the entire time asking each other questions and answering them. Eventually they started to sound like some horrible Buzzfeed questionnaire like "what is your favorite color?" After that, we broke it off and just went back to being friends. You can say that we "friend-zoned" each other, but between that time and Junior year of High school we got to know each other extremely well. We would spend hours texting and talking, which helped build our relationship before it even began. Over the years of being in the "friend-zone," we saw each other at our best and worst times. If you go into a relationship without knowing each other well, then moments when someone is at their worst might come as a surprise, whereas with us, we already knew how the other reacted and how to best respond to help each other.
People often forget that a relationship becomes more than just looking cute for each other and being on your best behavior the whole time. If someone doesn't like you when you don't wear makeup or fancy clothes or when you are having a horrible day, then a relationship isn't going to work out very well.
At the start of every relationship, people dress up, try to impress each other, and edit everything they text or say to each other. In my opinion, that isn't the best way to go about it. The person you choose to be in a relationship with should be your best friend. They should be the person you feel the most comfortable with and the one you can act the most normal around. Of course, it is polite and fun to dress up and impress each other, but you shouldn't completely change yourself or act differently to try to impress the person.
Relationships do cause people to act differently simply because you can't have the mindset of a single person if you're in a relationship, and relationships require compromises, but that doesn't mean you have to completely change your personality. If the relationship works out, then that person is going to see you at your worst and at your best; the real test of your affection for each other will be whether you stick around when times are bad as well as good.
Of course, you will always learn more about each other as new situations occur, but having a solid basis is, in my opinion, the best way to go about a relationship. The world we live in now doesn't always think about relationships, and of course people rarely enter one planning for it to last years, but after a period of time of dating you move past the "honeymoon" phase and you realize that this person is either someone you can see a future with or not. From my experience, I find that it's a lot easier and more likely to last if your significant other is someone who you see as your best friend and companion more than simply your "boyfriend" or "girlfriend."