To be blithesome is to be happy and without a care in the world. If you are feeling blithesome, you might want to skip or at least kick your heels up in the air.
When you're blissfully happy and don't have a single worry, you're blithesome. If you're blithesome, you're feeling carefree and not weighed down by burdens or anxiety. If you take the some off the end of blithesome, it will still carry the same meaning.