Do I go down an octave if I cannot hit the notes of the chorus?

I've been trying to sing Jonathan Estabrooks song, "share my voice" but once he hits the chorus I have to go down an octave because it's too high for me. Should i go down an octave or should I be trying to hit those notes?

Hi, Ariel! I think dropping the octave would be fine (if you had to perform this song today). But I do think it's valuable to practice as written (as long as you're not straining to reach those higher pitches). Are you able to sing the melody if you transition to head voice for the chorus?