Let's say you have been promoting some view (on some complex or fraught topic – e.g. politics, religion; or any "cause" or "-ism") for some time. When somebody criticizes this view, you spring to its defense. You find that you can easily refute most objections, and this increases your confidence. The view might originally have represented your best understanding of the topic. Subsequently you have gained more evidence, experience, and insight; yet the original view is never seriously reconsidered. You tell yourself that you remain objective and open-minded, but in fact your brain has stopped looking and listening for alternatives.
Here is a debiasing technique one might try: writing a hypothetical apostasy. Remind yourself before you start that unless you later choose to do so, you will never have to show this text to anyone.
Imagine, if you will, that the world's destruction is at stake and the only way to save it is for you to write a one-pager that convinces a jury that your old cherished view is mistaken or at least seriously incomplete. The more inadequate the jury thinks your old cherished view is, the greater the chances that the world is saved. The catch is that the jury consists of earlier stages of yourself (such as yourself such as you were one year ago). Moreover, the jury believes that you have been bribed to write your apostasy; so any assurances of the form "trust me, I am older and know better" will be ineffective. Your only hope of saving the world is by writing an apostasy that will make the jury recognize how flawed/partial/shallow/juvenile/crude/irresponsible/incomplete and generally inadequate your old cherished view is.
(If anybody tries this, feel free to comment below on whether you found the exersise fruitful or not – but no need to state which specific view you were considering or how it changed.)