Work out your own salvation??

I'm sure this verse has been discussed on here plenty of times but can someone explain these 2 verses:

12Wherefore, my beloved, as ye have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling.

13For it is God which worketh in you both to will and to do of his good pleasure.

Philippians 2:12,13 - What does it mean for US to work out our own salvation?

GOD is working within you to express His truth,
declare His love, and manifest His Holy Spirit.
You must work out what GOD has worked within
you!!