I used to body-shame my partner by saying something negative about her height, looks, etc. But then I realized that I wasn’t having fun with her, but instead at her cost and it started to impact her mental health. I immediately apologized to her and stopped.
Building open, clear and safe channels of communication in your relationship not only removes the stress and distance of guesswork, they also bring in fulfilment, empathy and a real chance of growth. Remember, no matter how well you know your partner, you can't read their mind.
Over time and after quite a few conflicts, I realized an important thing - I should keep the conversation focused on the issue at hand and not criticize my partner at the core of their character. That’s the difference between complaint and criticism.
As a couple, staying friends has always been important for us, so we have a lot of simple rituals that help us stay that way. E.g together we write inspiring, funny, and uplifting messages on sticky notes and leave them in unexpected places around our community.
Before speaking with my partner about what's bothering me, I usually let him know what I hope to get from the conversation. e.g "I just want to be heard", or, "I want your inputs on something and love for us to problem solve together", etc.
Having shared goals and working towards them together has been very helpful in keeping our relationship strong e.g saving for a vacation. Having something to work towards together keeps us motivated and gives us a sense of accomplishment.