Is it possible to look back on an event that you once said made you smile and feel disgusted that you could have thought so?

I was in a relationship in which certain behaviors were deemed acceptable. I said at one point that there was a memory that made me smile during my last relationship to the girl I was dating. I am in a relationship now that has made me realize there was a lot that was wrong with my outlook. I behaved in ways that were irresponsible and disrespectful. My current girlfriend feels I can’t change my mind about how I feel about my last situation. Do you think it’s possible to change one’s perspective on events in the past given what one has come to know/understand in the present?