Ever did something with the "best intentions?" It could be anything from a simple project at home to witnessing to a neighbor. You might be scratching your head on the witnessing illustrations.
Like it or not, we have the best intentions for everything in life. Even as believer, we think we are doing everything for the glory of God, but our motives may not even be pure. Going back to witnessing to the neighbor. You know the command Jesus gave to disciple all people from Matthew 28, but your intentions might be for your neighbor to know you are a Christian so they will not swear at you.
In his book, The Transforming Power of the Gospel, Jerry Bridges writes that "our best works are stained with impure (that is, mixed) motives and imperfect performance. We never achieve loving God with all our hearts and our neighbors as ourselves. As Augustine is quoted as saying, 'Our best works are but splendid vices in the sense they are less than the perfection God requires.'"
No matter what our motives or "best intentions" are, they will always be marred by sin. That is why you and I need the gospel everyday. We need to be reminded of the sheer grace of God that He has freely given to His children. When are "best intentions" fall short, His grace covers them. We need to be reminded that one day we will be saved from this body of death and not consumed with false motives.
Glory to God on the day that happens.