I wonder why I am always ________ and often leave my ho...

根据句意，句子中的‘I wonder why I am always _______ and often leave my homework at home.’是表达自己经常忘记事情。‘forgetful’是形容词，表示‘健忘的’。‘forget’是动词，不能直接用于此处，需要变为‘forgetful’来修饰‘I am’。