I did a psychology degree and am now (following a PhD, years as a researcher, etc...) a university lecturer.
First off, let me just say that whoever told you that Psychology is the worst degree for employment is talking out of their hat. Stats can be found here.
Now, some people get jobs after graduating, others go on to do further study, some are unemployed, and a few fall into other categories. I think that best thing to do is to look at the numbers who are unemployed. Here is a little league table from the latest figures:
Computer Science: 14.8%
Media studies: 13.3%
Fine arts: 12.0%
Electrical and Electronic Engineering: 11.7%
Design: 11.4%
Finance and accountancy: 10.9%
Physics: 10.7%
Biology: 10.6%
Economics: 10.3%
Business and management: 10.0%
Sociology: 9.9%
Politics: 9.8%
Mathematics: 9.4%
Marketing: 9.3%
Chemistry: 9.2%
Performing arts: 9.0%
Architecture and Building: 8.8%
Physical and Geographical Sciences: 8.8%
English: 8.6%
History: 8.6%
All subjects: 8.5%
Civil Engineering: 8.5%
Languages: 8.5%
Mechanical Engineering: 8.4%
Hospitality and Tourism: 8.2%
Psychology: 7.8%
Geography: 7.2%
Law: 7.1%
Sport Science: 5.6%
Psychology has one of the lowest rates of unemployment!
Second, there are all sorts of things that you can do with a degree in psychology. There are the 'Psychology' careers: academic, counselling, forensic, clinical, neuropsychology, educational, occupational. These all require further training and a BPS accredited degree. Psychology is also useful as a general degree. Most graduates do not go into jobs that use their degree per se. Rather, they end up in jobs that just require any old degree. This may as well be psychology. Psychology is also quite handy since it is a science subject (whatever anyone tells you, and ignoring the fact that the site I linked to above lists it as a social science, it is taught at universities as a science and is regarded by UCAS as a biological science - hence it's 'C' code) and teaches various critical thinking and statistics skills. Some people also seem to think that it makes you good at working with people, and so a lot of our graduates seem to gravitate towards HR.