How do you win back your boyfriend in one day?

Answer 1

You don't. If someone leaves because of a certain behavior on your part you must take action to improve and prove to them you are making efforts to stop the behavior. Make sure you think through it carefully because you don't want to change "who you are" for someone else. That never works. If they left because they are not happy and want to move on there is nothing you can do. Just like someone can't make you do something that you don't enjoy. Be honest, you would be really unhappy. Work on being happy with yourself and eventually you will find someone who is happy spending time with you.