Success (like getting a startup off the ground) takes a lot more than just personal skill/intelligence/hardwork- there's fortunate timing and circumstances, the hardwork and contributions of others, time and monetary investment of others, plain old chance luck. Recognizing that some part your achievements depended on others and things beyond your control both requires humility and can humble you.

That's not a bad state of mind, and it doesn't have to be just false modesty.