Are you happy today? What are your goals in life? Do you have anyone at all? Maybe it feels wild to say that you want to travel to the moon, but to be honest, isn't it better to aim for the moon and end up in Houston at the NASA Space Center, than to aim for your neighbor, and only get there?
We are often so afraid of aiming for the impossible, that we do not aim at all. Wouldn't it be better to start aiming for higher and more difficult goals. You will most likely reach your goal if you really work hard and with purpose, but the worst thing that can happen is that you don't manage it completely, but you will still get closer?
If your goal is to make sure that famine is removed from earth... you might not be able to make sure that everyone will have enough food, but if you still manage to help millions of people, it is still better than nothing. Do you see the point?