This is plagiarism, you just cant do this. Here are the parts I take issue with, ( Stevie Nick's Words are are highlighted in red, yours are in black)
Oh, god up in the sky Am I still young?
Oh, mirror in the sky What is love?
Can I sail through changing ocean tides?
Can I sail thru the changing ocean tides?
Cause I'm so scared of changing
Well, I've been afraid of changing
Where's that kid inside me
Can the child within my heart
Of getting old
I'm getting older too
It is fine to take some inspiration from a song, but when you start to steal whole lines then people start to notice and dig deep and suddenly all sorts of things appear, not just stolen lines, but stolen words used in context, the thought patterns etc...
You have even used the same strong structure and included lines in the exact same place of the song. I can only presume you were going to include the guitar solo in the same place as well.
Its a nice message, obviously not original but that's fine, its all but impossible to come up with an original message now. If you like the message then sit down and write your own song on it, don't take Stevie's song and just change 90% of the lyric, you need to change all of the lyric if you want it work and be your own song.