The Good Book Company has a growing list of solid books coming out lately. I want to recommend you check out a recent release: Serving Without Sinking by John Hindley. A blurb from the first chapter...
...this book isn't primarily about our service. It's mainly about Jesus Christ, and about His service. He said that He "did not come to be served, but to serve, and to give his life as a ransom for many" (Mark 10 v 45). He meant it. He was taken, beaten, tried, mocked, nailed, hung, cursed, judged, killed. He served. He loved.
So Jesus does not want you to measure your life by your service of Him. He does not want your service to get in the way of your love for Him. He did not come to be served by you--He came to serve you.
If we grasp this, then we will be set free to enjoy His love. And then, oddly, we will also be free to serve Him longer, harder, braver, truer than we ever could otherwise. This is joy, and we'll only find it in Christ.