If you feel insignificant, it doesn't mean it's true. If you feel like you don't contribute to the world, it doesn't mean it's true. If others around you make you feel like you don't do much for your world, it doesn't mean it's true.
If you rely on others to show you or make you feel your own self-worth, you are waiting for a failing source of affirmation. Other humans are flawed. Many can't see the good in others unless it is spelled out for them. If you are the one who usually has to spell out the good in you so some others can see it and stop thinking ill of you, then the problem is those people, not you. You are worthy, you are lovable, you are worthy of love, no matter what your contributions are to your life or to anyone else's life. You don't have to wait for the feeble-minded to grow a spine and get new glasses to finally see for themselves, without being spoon-fed, the greatness that is within you.
You are great. No matter how little you feel. You are important, needed, even if others make you feel your contributions are miniscule. They don't need to be able to see it, let alone affirm it for you. You are enough of an affirmation for yourself.
You are great. And God is Greatest. Turn to Him before and above all others.