Try to find a lover who remains calm even in an argument, someone who is open, communicative and supportive, because these aren't your greatest strengths in a relationship, and getting involved with another person who gets angry rather than opening up will only spell disaster for the affair. That's your tendency -- to misunderstand your lover and respond with anger, the cold shoulder or any of a host of other behaviors that aren't really conducive to resolving the issue. You've probably been through more than one relationship in the past that was marked by bad communication -- frequent misunderstandings, arguments, suspicions and hurt feelings.
You may have been possessive of your sweetie because you never felt like you could fully trust them; maybe you never felt as though you had a real handle on how they actually spent their time, and with whom. Good communication would have dispelled your insecurities, of course, but it's hard for you to communicate well with someone you love. You get irrational in a relationship and start acting instead of thinking, or listening. Learning to calm down and open your ears is one of your challenges in life.