This is especially a problem with “dreamers”, ambitious, high dopamine people. The amount of dopamine they feel skews their perception of the likelihood of success. Pursuing goals becomes a matter of “this would be great if it worked” instead of “can it work?”.
Ultimately the only question that matters is “does it work”, and I prefer asking myself the question “can I make it work” in the privacy of my own home before I risk too much in making it a reality.
This applies to doing a startup (only starting a startup once I have a working prototype) and to research (only pursuing a research career full-time once I’ve found success in research, since if I never do so I wouldn’t want to make it my day job!).