This is one of those questions that our grandmothers would not have understood. One of the most important changes in our culture has been the elevation of "how we feel" to be more important than "what we do." I remember, as a child, being told that my feelings did not matter, the grass needed to be mowed. How I felt about mowing the grass did not impact the grass at all. Our grandmothers had that attitude toward their marriages. They had duties to perform and dedicated themselves to performing those duties. They learned to take pleasure in accomplishing good for themselves and those they loved.
Ultimately, this is one of the keys to being an excellent wife. No one can be an excellent wife if what they do depends on how they feel, because they will often not feel like doing anything at all. They will not be diligent in their work, but will be spotty in their work. They will take care of things only when they are "in the mood," and that means they are self-focused, not focused on loving their husband or children. Facebook is more fun than laundry and a woman who spends her day on Facebook instead of doing what needs to be done is not an excellent wife.
Women are often told to "trust their feelings," but the Bible tells wives to "love their husbands." Your love for your family should be your motive, not serving your own desires. The excellent wife has many things that bring her pleasure, but they include the things that make her a great wife.
Your husband has days like this as well. He has days he does not want to go to work. What does he do on those days? He goes to work. There are days that he does not want to spend at Band concerts for the children, but he goes because he is their father. He has "blah" days, just like you do, but he keeps doing his job.
You should keep doing your job, filling your role (which is much more important than you think). A blah day is just another day, requiring a little more effort.
But love is always about effort.