Noun
an actuating force or factor
Source: WordNetDealing with complexity is an inefficient and unnecessary waste of time, attention and mental energy. There is never any justification for things being complex when they could be simple. Edward de Bono
Deep in the human nature there is an almost irresistible tendency to concentrate physical and mental energy on attempts at solving problems that seem to be unsolvable. Ragnar Frisch
Deep in the human nature, there is an almost irresistible tendency to concentrate physical and mental energy on attempts at solving problems that seem to be unsolvable. Indeed, for some kinds of active people, only the seemingly unsolvable problems can arouse their interest. Ragnar Frisch
You obviously don't really forget how to play the old songs; you just don't have to spend so much time convincing yourself that you remember them. Way less mental energy is spent swimming around in lyrics you've already written and chords you've already played. Jeff Tweedy
Mental energy is wasted in caste disputes and village factions. Mokshagundam Visveshvaraya
When mental energy is allowed to follow the line of least resistance and to fall into easy channels, it is called weakness. James Allen