Breakup

My girlfriend broke up with me last week. Some of it was due to that she has a much higher income than me and some of it had to do with me not being assertive, and that I never argued with her. She said she wants me to always be in her life and remain friends. I did not argue with her when she told me this or try to persuade her to change her mind, I knew it wasn't easy for her to do this, so I made it as easy for her as possible. When should I contact her again, and how is it possible to have a relationship with her again?