Why does 'let go' in Metta trigger panic and heart racing?

Let go is a term that causes an instant panic after this word my heart pumps faster and I am well in need of holding on to something. I feel as though I were losing my ground. Such a high physical fear is a manifestation of an outdated mode of behavior in which I unconsciously equate giving in with putting oneself in danger. What do I need to retrain my body to let go? My name is Pooja, DOB 23rd March 1994. Time: 1:10 PM. Location: Chennai.