There's just one letter, one blink, one breath of a difference between wishful and wistful. Wishful is dreamy, puppy-eyed, magical longing, while wistful is melancholy, pensive, despondent.
Every one of us has the capacity to feel wishful or wistful depending on the circumstances or mood at any given moment. Add a particular song to the mix and the feeling can turn in either direction, depending on the lyrics and melody.
In addition to music, I have a small collection of children's books that can have a definitive impact on my mood. Sheila Rae the Brave really helps me shore up my courage. Bread and Jam for Frances reminds me not to become too rigid or set in my ways. Frances can be rather wistful when she is watching her sister Gloria slurp spaghetti gleefully, while she is stubbornly set on Day 4 of eating bread and jam at every meal. Stanley and Rhoda remind me of the many different parts of my personality so I can call forth my inner Stanley or Rhoda when needed. And the Velveteen Rabbit teaches me the importance of being real.