The best leaders say “my fault” first and figure out the details later.

Taking responsibility quickly is not the same as knowing exactly what went wrong. Going first stops the search, and a group hunting for someone to blame is a group not working on the problem, which costs more every minute than the error did. Details can be sorted out afterward, once nobody is busy defending themselves.

If you have any real share of it, say so early and without qualifiers. Then move straight to what happens next. Working out the precise proportions can wait, and usually matters far less than it felt like it would.