There's nothing about letting go that makes it unique to the Buddha's teachings Sarathw. Anyone can practice meditation and letting go.
Only people trying to understand the Buddha's teachings make an effort to try and comprehend the Four Noble Truths.
"For a disciple who has conviction in the Teacher's message & lives to penetrate it, what accords with the Dhamma is this:
'The Blessed One is the Teacher, I am a disciple. He is the one who knows, not I." -