If you can't deal with rejection or selling people on your idea/yourself, then entrepreneurship is likely not the right path for you.

If it takes a few rejected applications to learn that, it is time well spent.

Sorry, I didn't make myself clear. Dealing with rejections takes time, you get distracted, you get sad, it kills time which can be put in much better use.

You can deal with rejections, but that doesn't mean you have to deal with rejections.

You can use the time to make your product better. Someone famously said "Be so good, they can't ignore you", being mediocre and spending time in those activities is not very fruitful.

don't apply to things because you might get rejected from them is certainly good life advice

I think they are talking about the time involved with the application and the associated worry and issues of rejection after rejection (on odds).