Most Helpful Guys
Every relationship has a "honeymoon period" at the beginning - typically about 6 months - where you tend not to notice (or pay attention to) any of the bad or annoying things about your partner, and where you are both probably actively working to improve your behavior around each other. That will never last at that level - it's like actually living in a fantasy, but the fantasy doesn't last.
You have to remember that you are a flawed human being, and so is your SO. He will leave his towel on the bathroom floor or you will leave the cap off the toothpaste and you will piss each other off sometimes. But that is to be expected, and you have to keep communicating and you have to be willing to make some changes even if you prefer not to.
You also need to do a lot of work at the very beginning - before you commit to each other - and ask a lot of questions about long-term compatibility - about your thoughts on marriage, kids, religion, finances, lifestyle, living location, morals, values, etc. And you have to actually pay attention to the answers, and if there are conflicts, you have to work them out in advance. You MUST NOT EVER assume that your SO will change their mind in your favor down the road.
Mutual attraction is important, and feels good in the beginning, but if you don't have long-term compatibility, your relationship will fall apart, and the only time to figure that out is at the start - because if you don't have it, you have to break things off and move on, no matter how strong your feelings might be in the moment.
For myself, 14 years this June.