One's heart is not in it:
某人的心在里面 ×
对某件事缺乏热情，或是不感兴趣 √
例句：
His heart is not in it.他最这缺乏热情。拓展：①take heart, 振作精神，鼓起勇气Take heart! It will be easier from now on. 打起精神来！从现在起情况就会好转的。②lose heart: 灰心I'll never lose heart even if I should fail ten times. 即使失败10次，我也不灰心。,
