There is an element in every writer’s life (it does not matter if he is an amateur, accomplished or any intermediate level writer) that can affect his work and emotions at the same time: The review.
There is no message without readers. To share his writing with the world is one of the basic purposes of any author; the alternative would be to write for oneself only, hiding our whole literary production inside a drawer. But the moment another person lays his eyes on those paragraphs that took so much work to be written (or that leave our feelings exposed) we are giving this other person the ability to encourage us or rip us apart with only a few words.
Since the moment we start trying writing we find out that this art form has a peculiar aspect: everybody thinks they are a critic. Everybody thinks they have the skills, knowledge and criteria to produce opinions, advises and corrections to what they read.
As a writer you learn to pay attention to well documented reviews only, which is why we become more cautious when choosing who has access to our unfinished and new works. We also start receiving manuscripts from acquaintances and fellow writers who understand that we are well prepared enough as to evaluate some aspects of their work.
After reading enough we develop a literary sense of taste. The more pages we read the more any good writing becomes evident and we can identify a text that is not all that good as well. The hard part is to know exactly what is it that is not working and how to fix it.