The words are about the saving power of Christ. This world says whoever wrote the lyrics (don't assume it was Amy) will never be good enough and that becomes the "shackles of fear". The author struggles to feed the hunger that is "burning deep inside of me". We all have that hunger and know exactly what is meant. Christ offers the answer with "arms outstretched" on a "bleeding tree", the cross. Abide in Him and He vows "never to forsake you".