Creating branches in git basically free and is easy to do. This has lead to the development of techniques like git flow and other branch related work streams, which are now commonplace in development.
If you have changed or updated a git repository and want to throw away your changes then a good way of forcing the lastest changes to run a combination of two commands. The first command is git fetch --all, which tells git to download the latest updates from the remote without trying to merge or rebase anything. This is followed by git reset --hard origin/master where git resets the master branch (assuming you were on the master branch) to become the version of the master branch you just fetched. Here is the two commands in full: