I found a friend and I am losing him

I finally found someone who cares about me and who I care about, but since I am used to getting hurt by people I can't control my mouth and I start saying rude things to him and distancing myself from him. I told him I would like to beat him up and that he would definitely lose, "You are a weakling" - I said. Hearing that from me made him so sad and insulted and I'm so sorry I did that. I want to apologise, but I am afraid it won't help, and he will never forget what I said that day. I don't want to lose him. His friendship means so much to me, even though it's been just 3 months since we became friends... What can I do to not lose him?