Sigmund Freud once wrote that the psyche is divided into three different parts.

The id, one half of the unconscious mind - selfish, childish instincts with which people are born. This is the inner-child, the irresponsible one – this is everyone's inner-Sherlock. Sherlock Holmes himself is almost all id.

Those with the strongest, most unrestrained ids can be seen as psychopaths. Children with id centred minds will develop conduct and behavioural disorders and express opinions and emotions violently and destructively.

The super-ego, Mycroft Holmes in other words, strives to control and perfect everything according to very strict morals (something people seem to think Mycroft lacks.) It is the inner-parent to the id's inner-child. The id's other half. People with, ironically, uncontrollable super-egos develop anxiety disorders and neurotic tendencies such as phobias.

Mycroft's main phobia is Sherlock related. He is terrified that one day Sherlock will do something stupid. He's terrified that things will be left as they are at present, with his younger brother's resentment left following him for the rest of his life.

Then there is the ego. This is the conscious part of the mind. The filter. The ego balances out the id and super-ego, allowing some of the instincts through along with the morals to counter their sometimes mainly destructive qualities. It is the referee of the mind; it forges an allegiance between to the two halves of the unconscious. The ego in this story is Dr John Watson, always fighting to keep the two brothers in check. Patiently, mostly, but eventually there will come a time when one oversteps the line.

Without the ego there would be chaos. Without the id there would be no instinct, no motivation. Without the super-ego there would be no control. Without John there would be no Sherlock, without Mycroft there would be no Sherlock.

Sherlock is constantly reminded of his own personality's failures.