eagerness; enthusiasm; fighting spirit
Describes a state of being mentally charged up, often with a competitive or determined edge. Can imply being overly keyed up or trying too hard, sometimes with a negative nuance of excessive zeal.
His pre-match eagerness backfired, and he couldn't perform to his ability.
It was a presentation that showed the enthusiasm typical of a newcomer.
You could sense the tense eagerness in his play.
The rookie showed obvious tension and eagerness from the very first game.
He approached the match calmly, without any nervous over-eagerness.
His nervous eagerness got the better of him, and he couldn't perform at his usual level.
気合い is the burst of focused spirit or energy one musters for a task, while 気負い specifically describes being tensely overeager, sometimes self-defeatingly so.
弱気 describes a timid, lacking-confidence mental state, the opposite of the keyed-up, fighting-spirit tension of 気負い.
Compound of 気 (ki, 'spirit, mind') and 負い (oi, the continuative form of 負う 'to bear, to be burdened with'). Literally 'bearing spirit', suggesting a state of being mentally charged or burdened by one's own enthusiasm.