Thoughts on Justification

I read this quote today in reference to Galatians 2:15-16.

" Faith does not merit God's acceptance;it accepts Christ's merit before God "

I just wanted to throw that out for your thoughts.

I just know that I am truly thankful that it is based on Christ's merit that I am justified before God, not based on my own merit.

So I wonder why do I try now to live based on my own merit?