Are there any hard-fast rules for when you should resign a game or when you should fight for it? For instance, in timed games I've realized if they are destroying me, but running out of time to do it (like, less than 30 seconds) I think it's worth it to make them play it out because it is hard (for lower rated players anyway) to play both accurately and fast.
Are there any well known rules for when you should just give up, or is it mostly up to you whether you think you can win or not?