Do nonreligious people seem self-righteous and ungrateful? Do they seem like they have all the answers and don’t need any help from anybody? I say no.
I don't believe that your religious views inform your day-to-day behaviour very much. IME, there are lots of ********, and also lots of very decent people, in all walks of life (apart from those in the dictator business I guess).
Your worldview influences your behaviour, and your practice inflences your worldview - but all of that is orthogonal to the religious bit.
E.g., if you tend to like people, you will say please and thanks and engage more, which in turn will make you feel better... regardless of what you think about god/s or the afterlife. And if you practice saying please and thanks, it will make you feel more thankful and help you like people more.
You can practice positive attitudes, and it will make you a better - and more successful - person. And some religious practices might be an attempt or a way to achieve just that. But you can certainly do it without religion - and conversely, religion for the most part doesn't keep you from doing so.