This is the tagline of 101cookbook blog:
When you own over 100 cookbooks, it is time to stop buying, and start cooking.
I like this line, it points out a good suggestion, learning must go along with pratising.
In Chinese, there's an old story tells this theory similary. In BC 256, a young boy was good at the strategy analysis on paper, and could talk well, seemed better than his father who was already a famous excellent general, so the king sent him to the front line of the war, but he failed in every battle. This story is called "be an armchair strategist" (纸上谈兵）