Time.

I can't hold on any longer
But you must so
These feelings keep growing stronger

They could become in something stronger than those ones, so you should control them until you can show them to everyone.

Echoes that deafen the mind
Don't let those echoes destroy your thoughts and feelings, they're all what do you have now.
Will bury my voice in their wake
They wouldn't. You're too strong to let them inside your mind and let them keep your voice in silence.