You're not a loser, you're a winner. You are being honest about how you feel - and it's understandable. He and the life you had with him are familiar, and you are facing the unknown right now. Even though you are happy to let go of certain things (and people), and excited about living your life on your own terms, there is always comfort in the familiar even when it is painful. That is a major factor in why people stay in abusive or less than satisfying relationships. It is always easier to go with what you know than to have to figure new things out and navigate strange waters.
Eventually, being on your own will be less strange and you will not miss him so much. But don't beat yourself up for feeling this way now. I think you are now heading toward wonderful things.