For optimum growth and development the seedlings cannot be fighting for space and nutrients. Did I accidentally damage a few, yes, but nothing to be upset about. Some people just cut off the seedlings to thin so they do not disturb the roots. I prefer to carefully work the seedlings and roots from the soil and transplant as many as possible. I loose a few, but not many.
The tomatoes and peppers are actually doing really well right now. Who knows how large these plants will be when it's time to harden them off for the garden!
I am disappointed with my broccoli and cauliflower seedlings. They appear to have gotten too warm and dry. I will need to start seed for them again.
From time to time you will have seeds that don't do well and need to be resown, but it's not very often. I usually start my seeds so early, there's still time to plant again.
I will also need to start some of my other seeds soon as well. Everything is moving in the right direction!