So what can you do? The obvious solution would be to get a number of different computers for all the different users. Whilst sharing a computer and using a range of different accounts you will be able to protect your data and ensure that not everybody will be able to access your things, you will of course be compromising the amount of time that you can spend on the computer. So buy two computers, and that problem is solved.
You could also just use the one account, if you do not have documents on there that you would deem as private. However, if you still want to share the one account then you could always password protect the documents that you don't want people to see. You can put passwords on folders within the computer which means that the individual using your computer will be able to access everything that isn't password protected. This would also mean that they will not be saving too many documents on the computer as they will not have their 'own space'. Consider all of this before making two accounts.