Robert Traill (The Throne of Grace), Works 1:175:
A Christian is always a needy creature; because he hath much work to do, and most necessary work, and all above his strength. He that hath most work, and least strength, is most needy of help: Phil. 2:12, 13, Work out your own salvation with fear and trembling. For it is God which worketh in you, both to will and to do of his good pleasure. If the exhortation or command had been without the argument, it had been discouraging. What can a man do about his own salvation? It is God that begun a good work in them, and will perform it till the day of Jesus Christ, Phil. 1:6. Put hand to your work; for help is near. As the exhortation, Work out your own salvation with fear and trembling, hath the height of duty in it; so the argument, For it is God that worketh in you, both to will and to do of his good pleasure, doth deeply debase man’s sufficiency, and highly advance both the sovereignty and efficacy of his assisting grace. And happy is that Christian, who can lay the weight of the command on his conscience, and can at the same time improve the encouragement for believing obeying.