You don't fix this. You made a mistake, and you have to accept and deal with the outcome of you ending all alone. If girl 1 has a little self-respect, she'll never take you back, and rightly so. And if you don't want to be an asshole, you'll spare her your arguments and your presence. An apology might be appreciated, but don't go ANY further than that, because any follow-up of 'I want to be with you again' will completely destroy your apology. But I think it's better to immediatly completely remove yourself from her life.

Move on. You're a young man; if you wanna be a real man start acting like it. Move on, improve yourself, and try again in a couple of years.