#the accuser

Carpentry usually involved cutting, whittling, trimming, sanding. All wasting processes. Then you also join two pieces together that were previously unrelated. The lady is the subject of the art piece. He's saying he felt he could only inspire other artists, rather than join them as his peers.

the fact he regrets his way of thinking shows he feels guilt over pulling apart the fibres of his students and refitting them, something he's known to have done to Rosa in gethsemane if you believe he's the one forcing her to use her gift, which is the entire reason the accuser is after him.