It's understandable that some of your older experiences may be hard to recall. Review the facts before your interview. It can be helpful to keep a copy of your resume for yourself to refer to during your interview, although certainly don't use it as a crutch.
Of course, you should never "fudge" any facts on your resume. The more truthful you are on your resume, the better you will be able to discuss your past experience during your interview.
It's very easy to get distracted during an interview, but not paying attention can cost you. Read on for the next common interview mistake.