The very quick answer to that question is, as long as you believe therapy will work, it will, according to almost every single study and experiment performed in the field of therapy.
Approximately 80% of all studies that have examined the benefits of therapy have found mainly positive results. In other words, most people (about 75%) who enter therapy seem to leave therapy in better mental shape than people who never had therapy in the first place. Much of the success of therapy depends on the length of time and regularity the person attends sessions. The more sessions, the better chance growth will occur.
The second most important variable in whether or not therapy will be effective is the relationship between you and your therapist. Unquestionably, when clients feel they have a strong relationship with their therapist they show more growth and health at the end of their treatment. Whether you choose the right therapy or therapist, the most important thing to look for is someone you feel comfortable with and with whom you can see establishing a strong relationship. Clients who felt most successful in therapy reported they felt their therapists were warm, genuine and empathic.
But the most important element that will predict whether therapy will be successful or not is you. If you are dedicated, committed and determined to work week in and week out, there is nothing that will stand in the way of your growth. Sometimes in the beginning of therapy things start to feel worse, because unresolved issues are coming to the surface. If you can remember that the therapist is there to help you through these times and that it will improve, you are well on your way to further growth. But if you aren’t able to attend one hour a week or one hour every other week or think you can be “fixed” in a week, then maybe this isn’t the time for you to start therapy.
Read Jeremy’s outline (in a .pdf) of his workshop on Experiencing Life!