As a startup founder, I've learned that there's a crucial difference between persistence and stubbornness. Persistence means you'll keep at it till you win. Stubbornness implies that you assume you are correct when that's not necessarily the case. The goal of a startup founder is to 'converge' to a problem/solution that the market wants rather than 'force their solution down someone's throat' (all too common in startup territory).
At the end of the day, startups grow because they are rewarded by the market for introducing efficiency in one form or another - and their rewards are a fraction of the efficiency they introduced. If your solution isn't improving market efficiency, no amount of 'stubbornness' is going to make it work - it's time to pivot.
Startups grow because they are rewarded by the market for introducing efficiency in one form or another - and their rewards are a fraction of the efficiency they introduced
It's very easy to make two wrong assumptions as a startup founder - “finding startup ideas is easy”, and "I'll build it and they'll come"
Mistake #1: “Finding startup ideas is easy”
It is true that there are a near infinite amount of problems you could solve and be rewarded by the free market for it. However, there are also an infinite number of tarpits that merely seem like good ideas. A good comparison would be the fact that there's an infinite number of natural numbers (1, 2, 3, 4, ...) however, if you were to throw a dart on the number line, your probability of landing on a natural number is near 0. It's somewhat of a similar case with startup ideas.
Unfortunately, it's quite hard to solve any such problems unless you specifically have been impacted by them - and it's nearly impossible to know you're going to be in a tarpit till it's too late.
Mistake #2: “I’ll build it and they’ll come”
Prior to starting a company, founders in tech are usually working with people where everyone has been vetted for skill. Neither are your coworkers paying you. However, selling to someone who has NOT vetted you is a couple of orders of magnitude harder. It's hard to convince someone that you'll be able to solve their problem. It's hard to build reputation. One way founders can tackle this is by building something in a domain they are known experts in - for example, a doctor building a product in the medical domain will likely be considered more competent than an engineer doing so alone.
This is also why Paul Graham suggests that you "do things that don't scale" in the beginning. You need to delight your initial customers or they'll give up on you - and you'll be left with nothing to build credibility with.
Credits to Paul Graham, from whose essay I’ve borrowed heavily.