Yea, stop acting like you have a high stress job and large uncertainty about if you will be successful. Ignore the fact that most startups fail.
"It's better to be prepared and not have an opportunity than to be given one and not be prepared." - My grandfather
For example, we are currently in a fantastic economic environment to found a startup. Raising money, recruiting talent, finding partners,etc is easier than ever before(at least in startup hotspots). People who are working on a project on the side part time and are waiting to take the leap into a startup until they're more prepared will likely miss out on the opportunity and will regret it later.
He's not saying that you shouldn't try to seize opportunities when you may not be fully prepared; He's saying when opportunities are available, you will be more able to seize it if you're more prepared.