A.T. Robertson Commentary 2 Corinthians 12:10

"Wherefore I take pleasure in weaknesses, in injuries, in necessities, in persecutions, in distresses, for Christ`s sake: for when I am weak, then am I strong." — 2 Corinthians 12:10 (ASV)

Wherefore I take pleasure (διο ευδοκω). For this noble word see on Mt 3:17; 2 Corinthians 5:8. The enemies of Paul will have a hard time now in making Paul unhappy by persecutions even unto death . He is not courting martyrdom, but he does not fear it or anything that is "for Christ's sake" (υπερ Χριστου).

For when (οταν γαρ). "For whenever," indefinite time.

Then I am strong (τοτε δυνατος ειμ). At that very time, but not in myself, but in the fresh access of power from Christ for the emergency.