How do we solve our problems without getting into any fights?

Hi sis dolly im a 30year old lady,for the past 9 months ive been separated with my boyfriend of 3 years and now we back together sgain and its been a month now,this guy used to cheat on me and we used to fight and argue most of the times,bt now since we are together again we seem to have grown up since well we knw how to communicate n solve our problems without getting into any fights,but im scared if he will eva cheat on again.