Raising money is the second hardest part of starting a startup. The hardest part is making something people want: most startups that die, die because they didn’t do that. But the second biggest cause of death is probably the difficulty of raising money. Fundraising is brutal.
One reason it’s so brutal is simply the brutality of markets. People who’ve spent most of their lives in schools or big companies may not have been exposed to that. Professors and bosses usually feel some sense of responsibility toward you; if you make a valiant effort and fail, they’ll cut you a break. Markets are less forgiving. Customers don’t care how hard you worked, only whether you solved their problems.