Communication is a HUGE topic, but let's go through a few basics:
My husband and I have formed a few rules whenever we're in a fight that have helped us from going too far and taking a disagreement to a big, personal hurt. You may like to use these rules too, or you may find some yourself. The easiest time to identify what your specific rules are is [unfortunately] after a particularly bad fight. Looking back together, try to identify when something got too personal or mean in the fight and when it turned from productive conversation to harmful. PLEASE try to REFRAIN from blaming or accusing. The point is not to start a new fight, but to share with your spouse how something made you feel. Look at #3 above!
If the pain point you identify is something that has happened before and that you know is very painful, you may want to agree that it is off-limits. Make your rule specific enough so that you would know if this rule is broken in the future. Knowing that it is a rule may help jolt you out of a bad situation in the future. When a rule is broken, agree to take a breath, apologize, and work on communicating a different way. The person who is affected should make efforts to forgive and let the offender try again.
So without further explanation, here are our rules:
More wisdom to be found at the Gottman Institute:
https://www.gottman.com/about/
And check out wisdom from Doug Hinderer:
https://www.happymarriageforlife.com/about
https://www.youtube.com/watch?v=wr2PuvQFLTA&t=2225s