"Only the nobility have ancestors. Most people only have grandparents!" - Pridefly, Ash Girl by Timberlake Wertenbaker.
"Pride comes before a fall", sez the old adage. It's better to be low-born and humble, than high-born and proud.
It's about half right. If you're considered low-born and humble for it, chances are you don't have anything to be proud of in your whacked world where class difference between the commoner and nobility class actually makes a difference - we tried that and the French Revolution happened.
Unless in excess, I see no reason for pride to be a deadly sin. I can see how it can be used as a deadly form of social control, though. If you want to keep a person down, tell them they have nothing to be proud of. That they shouldn't see their accomplishments as worth much. This can effectively prevent a person from asserting themselves, because part of what fuels our self-assurance in this world is our pride and joy tha comes from achieving, from doing stuff we're good at, from being ourselves.
If we can't be proud of these things, then our happiness would derive more from outside factors, often dependent on other people. So we stop making ourselves happy and dedicate ourselves to making other people happy, just to prop ourselves up.
Take away the pride one has in something specific they do, and you have a person who believes their unique talent is nothing more than a gift that isn't really theirs. They can never truly own their talent, because they can't take pride in it. And when they don't believe they own their talent, they become easily manipulated into doing stuff with their talent that they might not want to, if only to avoid the criticism that they are selfish with their skill which could be used for XYZ purposes.
We need to have pride. We need to know, from ourselves for ourselves, that pride in our skills, our accomplishments, our doings, our virtues, our selves, is an okay thing. Pride can help us uplift ourselves, that we can serve those we love so much better, because we are sure in ourselves and our capability to do things. Pride breeds in children the self-confidence they need to grow up happy, healthy mature adults, secure in their place in the world, that they will own it, serve it, change it as it needs.
For those packed with privilege, pride isn't really necessary at all. They've got all the cushion they need against the world, after all. But there's pride, and there's obnoxious arrogance, and whilst one can lead to the other, it doesn't have to.
So take some time out, and think about stuff you know you've done that was good, and be proud of yourself. You deserve that short reprieve from the rest of the world that's busy telling you how much you suck.