So I save thoughts for blog articles on my computer, and often when reading them back, at a later date, I decide the thought wasn't a good one, and I delete it. This process of delaying my posts, allows me to think through what I am writing, in a more responsible manner.
While I was attending Durham College, my art professors would say, "don't stick with the first thing that falls out of your pencil." In fact, we would often be required to make ten alternative sketches, before choosing the direction to take our art piece. We need to learn to be okay with throwing out work that is bad, and moving on from it to something better.
When I used to draw comics more frequently, I used to say, “the best thing to do on a bad drawing day, is to draw”. I jokingly said, I was “flushing the bad drawings out of my pencil to get to the good stuff”.
Sometimes we need to get bad writing out of our systems, to 'clear the way' for good writing. But it's important not to confuse the bad writing with the good, otherwise, we can get stuck on a poorly written piece and abandoned the true jewel in store, that's just around the corner.
Learning what is worth saving and what is not, takes time. Unfortunately, many people educate their taste by getting used to writing in an undeveloped manner. This is like a chef who cooks poorly, because of lack of exposure to better cooks, and gets used to the taste of poorly cooked food. He or she will start to make more poorly cooked food, since he or she considers this taste as "normal" or even "good." Surround yourself with good writing. If the writer's you read, aren't good cooks with their words, don't ruin your taste buds by sampling their confections.
In summary, don't be afraid to write what you are feeling, in order to get those feelings out. But similarly, don't be afraid to throw those feelings and writings away, once stated. Sometimes the process of removing or expressing those feelings, in this risk free way, is reason enough to write them. For example, writing about something that upsets you, can help you think through your feelings on the subject. But sometimes, those feelings weren't meant to be shared with other people, but instead, to be recognized and dealt with.