Don't be afraid to experiment with commands that rewrite history*. Git doesn't delete your commits for 90 days by default, and during that time you can easily recover them from the reflog:
$ git reset @~3 # go back 3 commits
$ git reflog
c4f708b HEAD@{0}: reset: moving to @~3
2c52489 HEAD@{1}: commit: more changes
4a5246d HEAD@{2}: commit: make important changes
e8571e4 HEAD@{3}: commit: make some changes
... earlier commits ...
$ git reset 2c52489
... and you're back where you started
* Watch out for options like --hard
and --force
though — they can discard data.
* Also, avoid rewriting history on any branches you're collaborating on.