You could be suffering from mild depression. You may have decent income, your family is okay, but you find yourself sad. You then feel guilty wondering why you feel like that when you have 'everything you need.' Do you find your work meaningful? Do you have a clear picture of your future? How often do you time to connect with nature? Any traumatizing event you've experienced in the past? Deeply ask yourself these questions and probably you may find your answers among them. Cheers.
We live in a sick world, look for the reason outside, not within you.