Paul is making an observation about life in this present evil age. Those who labor and strive in the “flesh” produced the works of the flesh - which is temporary…we all will leave these things behind!
"For you were called to freedom, brothers and sisters; only do not turn your freedom into an opportunity for the flesh, but serve one another through love... the works of the flesh are evident, which are: sexual immorality, impurity, indecent behavior, idolatry, witchcraft, hostilities, strife, jealousy, outbursts of anger, selfish ambition, dissensions, factions, envy, drunkenness, carousing, and things like these, of which I forewarn you, just as I have forewarned you, that those committing such things will NOT BE ENJOYING THE ALLOTMENT OF THE KINGDOM OF GOD." (Galatians 5:13, 19-21)
Works of the flesh will not be part of the Kingdom of God (the allotment). On the other hand, those who live their lives producing fruit of the spirit will continue to be rewarded with those fruits in the Kingdom of God.
"...the fruit of the spirit is love, joy, peace, forbearance, kindness, goodness, faithfulness, gentleness and self-control.” (Galatians 5:22-23)
So….
“Let us not lose heart in doing good, for in due time we will reap if we do not grow weary. So then, while we have opportunity, let us do good to all people.” (Galatians 6:9)
“Let us not lose heart in doing good, for in due time we will reap if we do not grow weary. So then, while we have opportunity, let us do good to all people.” (Galatians 6:9)