About the first kiss, I am a man, and I regret it. I feel like a loser now.

The reason why you gave your first kiss to that girl must be that you had a special experience with that girl. That experience must be beautiful, so try to remember the beautiful things when you meet, so that you can have one more friend. Why not? When kissing, you must really like each other, which is nothing to be ashamed of. Open your mind, don't care too much about the past, what matters is the present and the future.