Stuff gets screwed up. Any lawyer who says they make no errors in their practice is either lying - or that lawyer has never had any clients or cases.
Earlier this week I called a client to apologize. We had sent him wrong documents. It was not a big deal. No deadlines were missed. No confidential material was inadvertently disclosed. It was quite embarrassing, however.
When I called, the client was super nice about it, and he really appreciated hearing from us - especially from the man with his name on the door. (There are benefits to being the old guy.)
When mistakes happen - and, as noted above, they will happen despite your best efforts - what matters most is fixing or at least mitigating any damage done.
Equally important is being honest about it and, if necessary, advising the client accordingly. If it's a "no harm - no foul" situation maybe you get some leeway with clients, but the better practice is err on the side of disclosure.
The worst thing you can do is to try to hide a problem. I always tell young lawyers that I can easily forgive errors - even really big ones - I won't forgive trying to hide something that went wrong. That gets into "fireable offense" territory very quickly.
Fixing blame is also something that is rarely productive. The simple reality is that in a law firm the cause of most mistakes is multifactorial - as doctors so aptly like to say.
Figuring out what went wrong may be important; scapegoating never is. It's just toxic.
Another piece of advice I offer young lawyers is to never - and I truly mean never - try to dodge responsibility. "Not my fault" or "no one told me" are excuses with a maximum range of zero meters - as we would have said back in my artillery days. If you want to see me get mad, try that approach.
Even worse for any lawyer is telling third parties that some problem is the product of your assistant or paralegal. Even if there really is some issue with such characters, that should remain internal.
Bottom line:
1. Own your work. It's on you, good or bad. Always.
2. Be forgiving of your colleague's errors. All of us screw up at times.