The definition of stress:

You sit at your desk while desperately trying to write the first chapter of your thesis. As you are doing this you are dying for a mug of tea; hoping and praying someone (ie. your mother) will come in and offer one. In the meantime you have a full mug of tea sitting right in front of you on your desk which your mother placed there an hour ago and which is now stone cold. No need to say anything else. Stressed.