I don't know if I believe in them. I think they are useful, if not factual.
Doing hard things requires courage and determination apart from other things like hardwork and intelligence. Courage and determination are required to fight the risk. Risk is involved in all difficult projects. And that risk arises from the statistical fact that more people have failed in doing that than those who have succeeded. This indicates that on an average, it's wiser not to try anything risky, alias difficult, alias great, deed. A normal logic will always lead us to this conclusion.
The only thing that can break this argument is a self-image that 'I'm not normal'. And what/how I am trying to do is not normal. With that one can claim that in spite of the high risk, it's reasonable 'for me' to try it.
However, that self-image etc isn't based on reason. It's based on courage and determination.
Anything that boosts these is a useful thing. Good omens are such things.
I don't believe that they wilfully conspire to make things happen for our success. I think we conspire to interpret them that way. This conspiracy is rooted at our wish to do something good, extraordinary, great.