It's a sporting cliche to explain a loss of form by saying that some team or individual have "lost their confidence." The concept can, however, be justified and understood in neuroscientific terms. When a team or individual perform with confidence, then their actions are under the control of the cerebellum, part of the hindbrain, (the most ancient part of the brain in evolutionary terms); when confidence is lost, then their actions tend to fall under the control of the cerebrum, part of the forebrain. The distinction between the two types of control is beautifully explained by Roger Penrose:
The cerebellum...is responsible for precise coordination and control of the body - its timing, balance, and delicacy of movement. Imagine the flowing artistry of a dancer, the easy accuracy of a professional tennis player, the lightning control of a racing driver, and the sure movement of a painter's or musician's hands...Without the cerebellum, such precision would not be possible, and all movement would become fumbling and clumsy. It seems that, when one is learning a new skill, be it walking or driving a car, initially one must think through each action in detail, and the cerebrum is in control; but when the skill has been mastered - and has become 'second nature' - it is the cerebellum that takes over. Moreover, it is a familiar experience that if one thinks about one's actions in a skill that has been so mastered, then one's easy control may be temporarily lost. Thinking about it seems to involve the reintroduction of cerebral control and, although a consequent flexibility of activity is thereby introduced, the flowing and precise cerebellar action is lost. (The Emperor's New Mind, p490).
If a team or individual lose sporting confidence for whatever reason, perhaps even just because of some random mistakes, then this tends to provoke a conscious analysis of technique, which requires the intervention of the cerebrum.
There are, however, other causes for the intervention of the cerebrum. A change of conditions or circumstances can also be sufficient to trigger cerebral control. For example, at the beginning of the year, Grand Prix drivers Kimi Raikkonen and Fernando Alonso both struggled to adapt to the unfamiliar characteristics of their newly adopted Bridgestone tyres; as they attempted to change their driving styles, their form declined because their normal cerebellar control was being over-ridden by the cerebrum. However, with the passage of time, control returned to the cerebellum, and both Raikkonen and Alonso finished the season strongly.