**Is it possible to block out a bad time in your life?**
I am not a professional, but I don't think you want to "block out" anything. What you might be able to accomplish with hypnosis (self hypnosis) is to reprogram your subconcience mind to correct your anxieties.
Using imagery while doing self hypnosis is very powerful, but you have to spend time each day doing it. Repetition is the key. I have used self hypnosis and imagery to accomplish many things. I have posted about some of these things and if you're interested in reading about some of them click on the link to read all my posts.
The following snippet suggest that what you ask is possible.
"Fear reduction: People have overcome fears by watching others conquer the same fear. They even imitate others seen in a film mastering a fear. Just having vivid imagery of someone handling the fear we face may be enough to provide a new model of behavior for us to imitate. Also, hypnosis or imagery can be used to create a very relaxed feeling and then to imagine confronting the frightening situation (see confronting the fear and desensitization in chapter 12). "
Half of doing anything is just getting started, so read all you can about it to learn how to do it best and go for it.