True Self / False Self
The True Self and the False Self are ideas expounded by D.W. Winnicott.
The True Self is the parts of ourselves which truly reflect our inner needs and hungers.
The False Self, on the other hand, is the collection of attributes, behaviours, and values which we develop to allow us to smoothly integrate into the culture, community, and society around us.
For example, if someone insults us in a public place, then our False Self will tell that person how disappointed we are and that what he said is absolutely untrue. Our True Self, on the other hand, would thump the guy around the head a few times until he saw reason.
Likewise, our True Self might like to have us grabbing and then screwing that gorgeous girl (or guy) we see on the bus, but our False Self will cause us to limit our interaction with the gorgeousness to the occasional admiring glance.
While the False Self clearly has a place in preventing us from getting arrested or ostracised by our peers, if we use it too often then our true inner needs and hungers just don't get met. The problem is that in our western culture the requirement of having a False Self is drilled into us so much that we may come to think of it being in charge as the only way of doing things. This can cause frustration because other deeper, perhaps primal, needs are left to build up without any outlet. If not met these needs can leak out in different forms, such as irritability manifesting as road rage, snapping at one's partner, yelling, and kicking the dog.
BDSM provides safe and structured opportunities and context where the False Self can either retreat of its own accord, or be driven away temporarily, and the True Self can take over and express itself.