"efficiency has become weakened; they have lost what ability they had to do successful work for the Lord. Absenting themselves from the school of Christ, they have forgotten the sound of the Teacher's voice, and He cannot direct their course. CT 410.1"
"I am the vine, ye are the branches: He that abideth in me, and I in him, the same bringeth forth much fruit: for without me ye can do nothing."
The EGW passage echoes the principle of dependence on Christ for spiritual effectiveness, as highlighted in John 15:5.