After reading this roundup of research into the psychology of thought suppression you will see that the results are fairly conclusive: it’s counter-productive in almost every circumstance.
From research into substance cravings, so-called ‘intrusive’ memories, and even depression, thought suppression has been shown to not work and the act of remembering when attempting to suppress has been dubbed the ‘post-suppression rebound effect’. The article concludes with:
The irony of thought suppression, then, is that actively trying to manage our own minds can sometimes do more harm than good. Although it makes perfect intuitive sense to try and suppress unwanted thoughts, unfortunately the very process we use to do this contains the seeds of its own destruction. The more we try and push intrusive thoughts down, the more they pop back up, stronger than ever.
via Mind Hacks