JESS: Well, hurry – a mind is a terrible thing to waste.
A mind is a terrible thing to waste is the marketing slogan of the United Negro College Fund, adopted in 1972, and one of the most widely recognised advertising slogans in the US. Despite its name, the UNCF has scholarships open to people of all ethnic backgrounds, although the majority of recipients are African-American.
This is something said as a joke which is all too true. On some level, Jess must realise that he is letting his good mind go to waste, or that it is being wasted.
The Annotated Gilmore Girls 