Being submissive is more about changing communication patterns rather than changing yourself. We all have certain changes that are ideal to make to get along with another human being. See if this helps: making different opinions than his known only when you feel the subject at hand is very important. Also, neutralizing the tone that you deliver differing opinions in. Men will more often react negatively to a high-pitched voice when they don't like the statement itself. If you lower your voice to a more relaxing range you might find what you say does not sound as independent or opinionated. Finally, try asking for his opinion and taking his suggestion on things that you aren't really worried about. This way you seem more submissive or easy-going but haven't made any sacrifices.