You then, my child, be strengthened by the grace that is in Christ Jesus. 2 Timothy 2:1
“First, then, there is a call to be strong. Timothy was weak; Timothy was timid. Yet he was called to a position of leadership in the church – and in an area in which Paul’s authority was rejected. It is as if Paul said to him, ‘Listen Timothy, never mind what other people say, never mind what other people think, never mind what other people do; you are to be strong. Never mind how shy you feel, never mind how weak you feel; you are to be strong.’ That is the first thing.
Second, you are to be strong in the grace that is in Christ Jesus. If the exhortation had simply been ‘be strong,’ it would have been absurd indeed. You might as well tell a snail to be quick or a horse to fly as to tell a weak man to be strong or a shy man to be brave. But Paul’s calling Timothy to fortitude is a Christian and not a stoical exhortation. Timothy was not to be strong in himself. He was not just to grit his teeth and clench his fists and set his jaw. No, he was, as the Greek literally means, to be strengthened with the grace that is in Christ Jesus, to find his resources for Christian service not in his own nature but in the grace of Jesus Christ.”
John Stott, Urbana 1967. Italics original.
The grace of Christ is not an excuse for weakness; he is an endless resource for strength.