And let us not be weary in well doing: for in due season we shall reap, if we faint not.
This verse speaks of doing good. The apostles argued at length that such works cannot justify or sanctify anyone.
Justify: Galatians 2:16 Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?
In other words, our Christian life was begun in the Spirit by faith alone.
Being made perfect by the flesh indicates that you may be trying (just as the Galatians) to achieve perfection through your own efforts.
The Christian life is a relationship and not a routine. We must stop going through the motions and meet with the Messiah. As we grow in our relationship with Christ it will eventually get to the point where we make every decision based on Christ, and not on ourselves and our routines.