Most business advice is necessary but not sufficient on its own to achieve success.
For a business to win, you need to check multiple boxes:
Customer demand. "The hard thing" only pays off if people are actively searching for what you've built in sufficient numbers. Pick a hard problem in a market where there's already pull.
Founder/market fit. If you're going to do hard things, it really helps if you like the market you're serving. You'll need to show up every day and answer their emails, fix their bugs, and reset their passwords. Understanding your customer means spending a lot of time hanging out with them.
Unfair advantages. Most success comes from stacking every advantage you have: your skills, network, reputation, and passion. Pick a "hard thing" where you already have an edge.
A reason to switch. You can build "the hard thing" in a good market, with every advantage, and still lose if what you ship doesn't give people enough reason to leave what they're already using.
Runway. Hard things take time. Like Jesse said: "Not many people are willing to grind on something for that long." A big risk with startups is burning out or going broke. If you're bootstrapping, you should probably have another source of revenue to sustain you.
Distribution. None of the above matters if nobody knows you exist. These days, my friend Lars Lofgren says, "You either become the influencer, or you hire the influencer."