who wrote a poem that is comparison of a person as the one one true constant in my life like the star polaris?

Answer 1

Are you thinking of the letter in Message in a Bottle with Kevin Coster? "You are my pole star, my one true north etc..."

Answer 2

Many have said it or used it in one form or another, but in 1599, The Bard said it first:
Shakespeare, in 'Julius Caesar', has Brutus say "I am as constant as the northern star." Given the precession of the Earth's axis, was Polaris close to the celestial north pole ...
imagine.gsfc.nasa.gov/docs/ask_astro/answers/98020...