“Surely, goodness and mercy shall follow me all the days of my life. And I will dwell in the House of the LORD forever.” – {Psalm 23:6}.
These were words of David affirming his confidence in the LORD whom he had come to know as his personal Shepherd! While the enemy will keep your sins, failures before you, reminding you seeking to drive and leave you in despair. David teaches us to look to the LORD your Shepherd, and his view is one you must adopt.  It is as though you look over your right shoulder into what is behind you, your past and see the Shepherd’s goodness for your steps, and then look over your left shoulder and see His “mercy,” for your sin! Look back only to see His goodness and mercy! Goodness and mercy “follow,” the word means, “pursue.” Not a start, stop, occasionally, a “wish –so” but a Divine certainty, “all the days of your life.” Never a second in a minute, in an hour, in a day, in a week, in a year, is “goodness and mercy” not pursuing you and will so all the way to the Father’s house, having delivered you safely to Him. Some chase after goodness and mercy, for those who have the LORD as their Shepherd, His goodness and mercy chases after them! 
The Shepherd is good and  merciful and abundantly so! “But, what about my sin, when I look back?,” you may ask. The evil one seeking to torment your mind at times by the memories that haunt you, because you have a new nature, “In Christ.” Sin bothers you, satan beats you down,“But God…” has “blotted them all out!! “…having forgiven us all our  transgressions,  having canceled out the certificate of debt
consisting  of decrees against us, which was hostile to us; and He has taken it out of the way, having nailed it to the cross.”- {Col 2:13-14}. The word,“canceled” means “erase!” Like taking a hard drive out of a computer so there is no data, your sin record has been “erased!”
“All” your sin, past, present, future, is “erased,” through the blood of the LORD Jesus! There is no record, in Heaven of sin against you. His blood has erased it all! Always end with “But God…”   
The accuser will have you sin conscious, the Holy Spirit will have you Christ conscious and will always have you end with hope in Him! His blood paying for your sins, past present, future.  Merciful and good Shepherd! 
The evil one will remind you of your past sin, to seek to dishearten you and lose focus. The unbelieving conscience will, which needs to be renewed, and the unlove of others, will seek to remind to manipulate, keep you down,“But God…” has erased it all. Be Shepherd conscious!
The verses begins with,“Surely,” which speaks of the  Heavenly irrevocable, certainty. It can be read,“Only, goodness and mercy shall pursue me all the days of my life.” It is to look back in history, and see God’s dealings with you of, goodness and mercy! All the days, good days, dark days, all days included, goodness and mercy backing you up, at the Shepherd’s command! Two “body guards!” to get you all the way Home to the Father’s House where you will dwell with Him forever and ever. Now that is Good News to let your mind think on and soak in!
Your Past? “Goodness and mercy pursuing you.”-v6
Your Future? “ And I will dwell in the house of the LORD forever.” –v6
Your Present?- “The LORD IS my Shepherd I shall not lack!”-v1
God’s Got Your Past, and Your Back!