Why does Douglass say learning was a curse rather then a blessing?

I believe that Fredrick Douglass meant that learning was a curse because slave owners wanted them to remain unlearned so they could maintain their dependency and this exercise more control over them. therefore having this skill which he could not practice openly must have been a type of mental abuse also being literate caused him to have a bigger view of the world which will tend to disturb any personal contentment which might be afforded by ignorance