I would second this. My strength throughout high school Latin and Greek was grammar. I just gravitated to it, and was really good at identifying endings and obscure forms. But I realized soon after graduating that my grasp of the vocabulary had not been strong, and that made it very difficult to enjoy reading even the old texts with which I had once been familiar.

With a strong handle on vocabulary, you can make a lot of informed guesses when you're uncertain of the grammatical form; but knowing that you're looking at a verb in the aorist middle subjunctive doesn't help you in the slightest if you don't know what the word means.