When a person becomes disturbed in his heart by seeing lightning in the sky, by seeing a ferocious animal or by hearing a tumultuous sound, his state of mind is called apprehensive. In such a state of apprehension, one tries to take shelter of something which provides safety. There may be standing of the hairs on the body, trembling of the body and sometimes the committing of mistakes. And sometimes the body may become stunned.
In the Padyāvalī there is the following statement: "My dear friend, Kṛṣṇa's residence in the demoniac circle at Mathurā, under the supremacy of the king of demons, Kaṁsa, is causing me much worry." This is one instance of apprehending some danger to Kṛṣṇa in ecstatic love for Him.