Hi, I know this is three years ago, but in case (like me) someone is looking for help on this. Your project is likely too big or too complex, so you need to go into your catalog, and go into each folder to delete everything you don't need (i.e. maps, toolboxes, databases etc.)
This is what solved it for me (there were unnecessary folder connections). It also doesn't like geoprocessing history items with errors, so delete those as well.