It's better to accurately believe you are smarter than others, than to feel ashamed of thinking so and repeatedly tell yourself you aren't smarter than anyone. That causes you to know what you tell yourself is a lie, and suspect the secret truth is that you're actually way way smarter than others, but you've been hiding it from yourself. Which is even worse.
Aim for accuracy.
But when aiming for accuracy, remember that a lot of other people are biased about how smart they are, and if you learn about them you'll realize that they are surprisingly similar to you and me. Most people are biased in overestimating themselves, and this bias is often very invisible.
Also, being smarter and altruistic does not make you superior or worth more. If being smart actually makes you worth so much more, maybe babies are worthless and a superintelligence should kill everyone. To me intelligence is like money, it's mostly a means rather than an end.
Being altruistic does not make you worth more either. We only evolved to be altruistic because it improves social standing. Evolution only allows us to try helping as many people as possible in a utilitarian way, because evolution knows that someone trying to do so can easily be biased and deceived into trying to maximize their power and having a lot of reproductive success as a "side effect." It's like in Terminator Salvation, the machines realize the best way to disguise a machine as being on team human is to put an actual human mind inside it, and try to steer him into serving their interests.
Altruism is good, but an altruistic person isn't worth more because their altruism is just a glitch within a selfish survival machine.
Meanwhile all creatures in the world are overtly selfish since there is no need to pretend altruism. But they are still beautiful, nature is still beautiful, and they are lovable creatures who deserve joy and wonder.
go find people who are better than you by a lot. one way to quickly do this is to join some sort of physical exercise class e.g. running, climbing etc. there will be lots of people who are better than you. you will feel smaller.
or you could read research papers. or watch a movie with real life actors who are really good at acting.
you will then figure out, as @Algon has mentioned in the comments, that the narcissism is load-bearing, and have to deal with that. which is a lot more scary