• at the back of one's mind
• juice of sg, moving spirit, prime mover
• he is the pivot of the team
• ardent, eager, ebullient, enthusiastic, expansive, keen, rapturous, soulful, warm, wholehearted, zealous
• to animate, to buck sy up, to buck up, to fire, to flush, to harangue, to inspire, to stir, to uplift, to warm up