Grace: noun poise, elegance, fitness, suppleness, agility, nimbleness, In other words everything that is professional, refined, and the best quality. A ballerina is graceful because of her strength and training.
A butler practices refined manners to show forth his grace. And then there is the grace that means of good favor. "She fell from grace." Grace can also mean a suspension, deferral or postponement or a blessing.
So when Paul says to Timothy "be strong in the grace that is in Jesus Christ," he is referring to Christ's ability to: bless him, defer judgment on him, act in an elegant and refined manner exhibiting a strength of character.
If we know that we are loved. If we know that we will be forgiven for our mistakes and that the goal that we have in sight is not lost to our shortcomings, then doesn't it give us a greater sense of strength?
Paul wants Timothy to always look to the standard, the love, the beauty, the example, and most of all the forgiveness that Jesus Christ has given to us. In a world where perfection brings reward, Jesus Christ offers solace for our acceptance of his love in our lives. He offers us his grace. When we are weak, he will carry us. When we are alone he will comfort.
vs 3 a good soldier of Jesus Christ - Soldiers do not have it easy. There is little time for pleasure or comfort. endure your hardness as if you were in a war for a noble cause. For Jesus Christ is a noble cause.
vs 4. entangleth himself with the affairs of this life. - If you are going to be a soldier of Jesus Christ then you must not worry about the frivolous things of this life, but rather choose to please the Lord Jesus Christ