When we become a Christian that is what our old life is to be to us. Paul mentions what our old man was like and smelly behaviors of the rotting old self we should get rid of.
Our lives are like a sweet smelling aroma to God. Yet, when we are still holding on to the old dead life of sin it can't be a pleasing smell. It probably be like grass to me where He can't inhale, or the smell of the dead rat that you don't want to inhale the smell.
How do we get rid of the smell of death?
Repent - Confess and turn away from the old life. This is what covers the smell like the rat that was sandwiched between the grass trimmings.
Stay away from evil habits - Like I have to stay away from grass the same with the things that are not of God we have to keep a healthy distance from it.
Accountability - Find someone that will help you stay accountable. Someone that will help you stay on track.
Prayer - True confession is part of pray but we also need to ask Him for His strength and power to resist the devil.
Then we can walk in the newness of life which we will talk about next.