2 Corinthians 11:30

‘If I must needs glory, I will glory of the things that concern my weakness.’

So if he is to boast he will boast about the things which show he is weak, He does not glory in his splendour like his opponents do, he glories in his weaknesses which show him to be a sharer in the sufferings of Christ (2 Corinthians 1:6), and one who can come alongside people in their weakness. They demonstrate that he carries the cross daily (2 Corinthians 4:10-11; 1 Corinthians 15:31). They demonstrate that he is willing to endure for Christ as a true and faithful servant.