It may happen that you accidentally lost a commit. Perhaps, you force-deleted an incorrect branch that you were to be working on, or you rewound the branch to an incorrect place, or you were on an incorrect branch while starting an operation. Assuming something like this happened, is there any way to get your commits back and to undo the mistake?

Because Git does not delete objects immediately, but keeps them for a while, and only deletes them if they are unreachable during the garbage collection phase, the commit you lost will be there; you just need to find it. The garbage collection operation has, as mentioned, its own safeties; though...