Human frailty is a condition that we have to acknowledge that is a reality in our lives.
No matter how healthy we are, we will fall sick now and then or feel pains here and there.
Even in the spiritual aspect, we are also frail as we succumb to temptation and sin.
But St. Paul would say that when he is weak, then he is strong.
It means that he admits to and acknowledges that he is weak, both physically and spiritually, but it is Jesus Christ who gives him the strength to run the race to the finish and keep the faith.
The 1st reading mentions of great biblical figures like Gideon, Barak, Samson, Jephthah, David, Samuel and the prophets.
They performed great deeds, but it also said that they were weak people who were given strength by God to carry out the marvels of God.
The man in the gospel who was possessed by an unclean spirit was also weak but cleansed of the evil, he was commissioned by Jesus to go and proclaim all that the Lord in His mercy has done for him.
Yes, it is when we admit and acknowledge that we are weak and sinful that the Lord comes to our help to give us strength.
Then we will be able to go forth and accomplish the marvels of God.