i rekon you have been a little harsh to it myself.... but in any case just do what i do....
... if a tool you have cant do the job you want, buy the bit you need!! In your case buy a 3/8" 12mm socket of a reputable brand.
Were you holding the wobble extension bar straight with your spare hand. Too often i see people incorrectly applying force to their ratchet spanner by just pulling the handle with one hand. This applies force to the bolt on only one side as the socket is not only trying to TURN the bolt, but to LIFT OFF the bolt head as well.
When i do it, i have one hand hold the socket straight, and the other pull back on the handle... much in this way:
See how one hand is pushing the handle end, whilst the other keeps the socket vertical by pulling back??