One more mark of growth in grace, is increased ZEAL and diligence in trying to do good to souls. The man who is really growing, will take greater interest in the salvation of sinners every year. Missions at home and abroad, efforts of every kind to spread the gospel, attempts of any sort to increase gospel light and diminish gospel darkness — all these things will every year have a greater place in his attention.

He will not become "weary in well-doing," just because he does not see every effort succeed. He will not care less for the progress of Christ's cause on earth, as he grows older, though he will learn to expect less. He will just work on, whatever the result may be — giving, praying, speaking, visiting, according to his position — and count his work its own reward. One of the surest marks of spiritual decline — is a decreased interest about the souls of others, and the growth of Christ's kingdom. Would anyone know whether he is growing in grace? Then let him look within for increased concern about the salvation of souls.

source: www.jcryle.info