It's good that you are recognizing the need to take responsibility. Most people need to be shown through actions rather than just words that an apology is sincere....so do not panic if it takes time before you start seeing results, but I promise you that patience with the process can go a long way and benefit you and your relationship significantly. Expressing your feelings and apologizing that you have gone too far is a start. Writing an apology too can be a meaningful gesture.....getting a blank card to write a sweet message on, maybe taking her to dinner or making dinner if you want. Also, simple statements like, "If I could take it back and act differently, I would have." Or maybe tell her what you would have done differently if a conflict were to arise between the two of you since nearly every couple has arguments from time to time.

I am uncertain how long it takes for her to cool off, but it is normal if for a little while things seem strained for a while. In most situations, partners move on to accept this and things get back to normal with a little bit of time. If not, maybe a few couples' therapy sessions might be helpful, or she can sit in a session with you if you go to therapy.