Sometimes talking is the way to find the solution. I appreciate that you have talked at length to a friend about the issues and she has given you good advice, but as you can see, that is not always enough. I would recommend that you take it one step further and talk with a therapist. It sounds like you might be experiencing some depressive feelings which could account for the guilt, regret and detachment. Seeking help from a professional can help you not only “move on” from the past, but find benefit in the experiences. Working through the past in a way that you can learn and grow from is different than just rehashing it and feeling bad about lost opportunities. You may benefit from the book Getting Past Your Past by Francine Shapiro.
I also encourage you to find ways to engage in the “here and now.” Sure, lots of people enjoyed their teens and twenties, but I have met just as many people who were late bloomers and found much more enjoyment in later stages of life. Much can be learned from the Buddhist philosophy that the past is over and the future has yet to arrive, so the only thing that is real is the present moment.
All the best,
Dr. Holly Counts