have one's feet on the ground 脚踏实地

【例句】
She is a girl who has her feet on the ground.
她是个脚踏实地的女孩子。

Jack always talks big about his future plan. Actually he should have his feet on the ground.
杰克对他的未来计划总是爱吹牛。实际上他真应该脚踏实地、实事求是呀。