"...Work out your own salvation with fear and trembling; for it is God who works in you both to will and to do for His good pleasure." Phil. 2:12-13 Notice it is Paul who confirms that salvation comes through faith, "...work out your own salvation with fear and trembling" you need to express an aspect of faith, surrender, investment and sacrifice (hard work).
Faith is not immediate trust but, permanent trust: living trust, magnificent, and "watchful". Our salvation is a miracle from God that "works in us", and for that reason it requires all of our attention. Working "with fear and trembling" means being conscious that every moment should be an investment in our relationship with God (as in a marriage), because God is working in us at every moment.
Fearing God means loving him irresistibly... in these 21 days may we learn, be renewed, invest and show attitudes of love toward Him.