Long wrote, “The High Self is said to lack mana (or vital force or life force energy) because it has no physical body, and to depend on the low self for what it needs in its ordinary activities when away from the lower man. When we are asleep it is supposed to touch us and take a little mana (or life force energy), but for the heavy changes needed to work in the materials of the dense or physical world, much mana (vital force) is needed.” What can Creator tell us?

This is a misguided understanding of the independence of the higher self from the physical level, the physical being you experience as an incarnated human. You are tethered to your higher self, but it receives its energy for existence from the divine realm via your soul, so it is not dependent on any kind of vital force or life force energy coming from below, it is more, again, the opposite, that the higher self can regulate the life force energy sent to the physical body, and the energy layers it comprises, and so it is a gatekeeper seeing to your welfare, physical life support from moment to moment, and has an important role in adjusting things as needed in a dynamic fashion when called for. So in moments of stress, high energy demands, and severe emotional disturbances, the higher self will send more life force energy to meet the local needs so you have energy to work with to deal with a crisis. It is true there is an interaction during sleep by the higher self. It has a role in body maintenance which is largely enacted during the sleep time when there is a physical quiescence. That is when much repair is done for ongoing maintenance, replenishment, reconstitution, and some resolution of difficulties from the prior day's events so that memories are consolidated for long-term storage if warranted, and many things of a trivial nature are let go of as unneeded, and so on, but it is the higher self that is more running the show than the body in terms of source of energy and its applications.