I found out the hard way as well with one of my cities. Instead I've been shrinking down the specialized areas and moving in general goods and offices with good results. Remember with offices, you need an educated population otherwise you'll get not enough works icons.
Actually not enough works is lack of unemployment. The game wants 5+% unemployed or workers won't work.
Unless you meant not enough educated workers, in which you'll need more education, usually higher education.
For all intents and purposes, you should have max education at all time as it provides many benefits.