That's a question that I have often pondered. How success is defined can greatly influence the path we take in our lives.
The natural human fleshly tendency is to relate success to numerical increases in things that we can number. More income, more popularity, etc. But for someone who labors for the Lord, the answer can be quite different. I say "can be" because in His providence, the Lord CAN provide large increases in these things. Abraham is a prime example of a goldly man whom He blessed with riches and influence. However, we make a fatal mistake when we automatically consider such increases in our lives to be blessings from God when in fact they could be stumbling blocks that the devil has placed in our path. The devil can "bless" too, and he knows how quickly most of us are likely to attribute our "successes" to God's favor.. even when we are living outside of God's will!
The words of Jesus come to my mind, when He told us to enter the strait gate (Mat. 7:13) and warned us that wide is the way that leads to destruction. Numerical increases of wealth or influence should be carefully examined to see whether they are from God's favor as we stay faithful to Him, or merely a devilish appeal to our "pride of life" (1 John 2:16). Finding success in God's eyes often means following a lonely, unpopular path that few are willing to pursue. It is the path to do what God has called us to do with our gifts and our lives regardless of the outcome, numerical or otherwise.
My greatest inspiration comes from Jesus, who died poor, naked and deserted by everyone when He went to the Cross. And yet His story is the greatest success story of all time! Think of all the millions of souls that will spend eternity in Heaven because of His faithfulness! In a much smaller way, God knows that as we stay faithful to Him in the little things He has called us to do, we may reap a spiritual harvest that can't be measured by mere numbers. So be encouraged as you labor for the Lord today, no matter how you measure your success!