You aren't alone! I have found myself nodding off when I am working on a project that has a simple and repetitive stitch. Latey I have had to just set those aside and do them while I am watching TV or talking with my kids or DH. I also find that if I am sleepy (or trying to carry on a conversation) NOT to do a complicated stitch or pattern, otherwise I spend more time learning to frog and tink!
Like the chocolate suggestion...always love to have a reason to nibble on chocolate!