Words and Phrases

Some days, the words are quite prolific. Other days not all that terrific. Some moments the words and phrases race while other times barely proceeding at a snail's pace. Today, they are somewhere in the middle. Tell me why can anyone answer this riddle? For awhile there were years of constant writing then came the gaps most unfilled as if thought and expression were dieting. The rhyme and the rhythm seems to come and go like the weather sometimes hot sometimes cold.