career pressure..

your boss gave you the responsibility because he trusts that you will do good with the tasks your officemate left off. he knows that you are well capable of accomplishing the output required or even better. just be positive about it. you learn a lot of things when you are given bigger responsibilities. you learn to be more patient, be more flexible and be good with time management, plus you're increasing your points on being one of the most dependable employees in your company. getting yourself on the negative side hinders your productivity. worrying won't do any good. believe you can do it :)