Take a cue from Marilyn--who looks so happy here with husband Arthur Miller--and tie a kerchief under the neck. To avoid the frump factor, make it a whispy chiffon, as here, or a gorgeous silk. Team it with cool sunnies, like Marilyn's Wayfarers.
Most importantly, smile like you're in love. The worst hair day in the world is no match for a heart wide open to happiness.