Stupid question on getting branch from yesterday

I have not yet figured this one out: I have not tagged anything, but know that I checked in something lame sometime between now and two days ago. How do I get my working repo to be that as it was, say, yesterday?

Do I do:

% git log --since="2 days ago"

parse, the output for the commit I want, and then do

% git reset <SHA>

or would I do

% git reset --soft <SHA>

or something else?

Bill