I have a problem and I need some advice on it?

me and my boyfriend have been going out for a bout 4 days now , and one night when I was waiting for him to come on from work i was flirting on myspace though comments ( it was something stupid that I only cont. doing because of the guy I was talking too) but anyway he read them and when he ask me about them I explained and he forgave but I still feel horrible what can I do to show him that I won't do it again ?