Note 2 at Acts 20:19: Paul in a sense was bragging on his own humility. That does not fit most people's teaching on humility, but it's our teaching that's wrong, not Paul's example. A person can be humble and know it. Consider that Moses wrote of himself as being the meekest man on the face of the whole earth (Num. 12:3).

Note 3 at Acts 20:19: There is only one recorded instance during Paul's three year stay in Ephesus (Acts 20:31) where Paul was openly attacked (Acts 19:23-41) and that was by Demetrius the silversmith, not the Jews. Therefore, it is certain by Paul's statement here that there were many persecutions which he endured which were not recorded in scripture.