We are predisposed to believe whatever is more negative. Someone tells you four good things and one bad thing, that bad thing is the thing that sticks.

Someone tells you you're doing a terrible job, but you feel like you're doing okay?

You'll believe the person.

Someone tells you you’re doing a great job, but you feel like you're doing terrible?

You'll believe yourself.

Negativity bias has a lot going for it: You're unlikely to overestimate your abilities, for example. Which means you're far less likely to trip over your own ego.

You're also far less likely to be the person you could be.

Find a balance, sure. But when dealing with biases, finding a balance means you need to actively compensate for those biases.

In short, try to believe more of the good stuff about yourself.