Della, when you invest your energy into something, how do you get it back?
Nobody told me there would be a pop quiz! *LOL*
Actually, energy itself cannot be reclaimed anymore than one could step in the same river twice. Energy is always moving, changing, transforming. And it is infinite - probably the only TRULY infinite thing in the universe, since it really is the ONLY thing in/of the universe. *heh* And it's BECAUSE energy is infinite that attempting to reclaim energy from the past may not be an entirely "sound" practice in the big picture. Point being - energy is all around us, so the energy that has been used in the "past" (tricky terminology there) is no more "trapped" than the water that flowed through the river 5 years ago is "lost". It is simply a matter of perspective & perception.
Now, to be more specific, with regard to the warrior path, when I discover that I have some sort of attachment to something that happened 10 years ago (which would be virtually impossible at this point), the simple awareness of that attachment is usually more than sufficient to release the attachment itself. Difficult to wrap words around it, but to use a specific example, I know a lot of people who strongly identify themselves as "an abused child" or "the adult child of an alcoholic", or any one of a thousand other labels. For myself, I would technically qualify as "an abused child", but the DIFFERENCE is that I literally opened my eyes one day and said, "That was then, this is now." And that was simply that. How could I BE "an abused child" when I had become a warrior? It wasn't possible.
To be brutally honest, what I have noticed is that people who carry that kind of baggage with them normally do so as a means of self-identity. The "abused children" I know who are now adults literally define themselves by how they were treated 20-30 years ago, and so they are actually LIVING in the past because they have never taken the steps (physical/emotional/spiritual) to move beyond their own baggage. If the person isn't a warrior, perhaps this is just normal human behaviour, but for a warrior it is simply not possible to go on carrying that kind of weight when it is far, far simpler to release it with the awareness that it is the baggage belonging to what amounts to a dead relative. The phantom past self is not the person I am in the Now.
Once that is wholly realized, a lot of the energetic attachments to the "past" will fall away quite easily & naturally. And if other (more deeply buried) attachments are discovered later on, the warrior may look at them with detachment and say to herself, "That was then, this is now."
I once knew a young man over at my Delphi forum who had spent COUNTLESS hours, months, years in recapitulation, only to discover that he was no better off than when he first began the process. And though a lot of die-hard Toltecs may not want to hear this, it has been observed that the ritualistic practice of recap CAN cement those attachments even deeper, as opposed to allowing the warrior to release them. I suspect the reason for this is that if a warrior begins practicing recap prior to losing self-importance, the SI itself could serve as a heavy gravity to the past, so this is yet one more reason why I insist that Toltec is a SYSTEM of Knowledge, and not just a bunch of loosely-related techniques to be practiced willy-nilly. *LOL*
So when you ask how do *I* get back energy invested in the past? I don't. I simply release it to the past and summon fresh energy in the Now. In that manner, I am moving *with* the natural flow of energy.
One of the exercises I occasionally do in my workshops is getting people to sit down with their phantom past self and really *see* that the person you were as a child or a young adult is not the person you have become. For most who are on a spiritual path, there is some moment or incident or at least an awareness of a "delineation" - i.e., "pre-path" and "path", just to use that terminology. And for many of us, there is a second delineation between "warrior" and "sorcerer", or between "warrior" and "wo/man of knowledge." When we can *see* those delineations, we begin to more clearly realize that we are constantly emerging from one chrysalis into a new form of being.
I rather doubt that the butterfly spends much time recapitulating the caterpillar.

Once that is understood, the "teflon warrior" approach to recapitulation generally becomes the natural way of things.
Of course, that's just me. Your mileage may vary.