A.T. Robertson Commentary Acts 26:2

"I think myself happy, king Agrippa, that I am to make my defense before thee this day touching all the things whereof I am accused by the Jews:" — Acts 26:2 (ASV)

I think myself happy (ηγημα εμαυτον μακαριον). See on Mt 5:3 for μακαριος. Blass notes that Paul, like Tertullus, begins with captatio benevolentiae, but absque adulatione. He says only what he can truthfully speak. For ηγημα see Php 3:7; 1 Timothy 6:1 (perfect middle indicative of ηγεομα), I have considered.

That I am to make my defence (μελλων απολογεισθα). Literally, "being about to make my defence."

Whereof I am accused (ων εγκαλουμα). Genitive with εγκαλουμα as in 19:40 or by attraction from accusative of relative (α) to case of antecedent (παντων).