From The Jedi Path by Daniel Wallace:
Trial of Spirit Tests a Jedi’s ability to vanquish inner battles and emerge unscathed.
Outsiders think that the Jedi exist to crusade against enemies–that we are mere counterbalances to the threat of the Sith. Only among our own ranks do we recognize that being a Jedi is an emotional commitment to a higher spirituality. This is the challenge represented by the Trial of Spirit, known among some as Facing the Mirror.
Jedi possess great power, and those who have fallen to the dark side have unleashed their power in waves of misery. The Trial of Spirit measures your temptations and whether you can put them aside in the service of a greater cause. Although this is just as much a battle as the Trial of Skill, during this challenge you might not flex a single muscle. The battlescape is in your mind, and victory is marked by a profound sense of peace.
It is impossible to describe the Trial of Spirit. I do not know the fears coiled in your heart. Not even Grand Master Fae would presume to dictate your challenges. The Trial of Spirit is to be carried out under deep meditation, with a Master who will nudge you onto the path that you least wish to tread.
Under meditation you may feel that you’ve been transported off Coruscant entirely. You may see the faces of colleagues who have long since passed into the Force. You will undoubtedly see things that disturb you, from enemies you have faced to the most horrific cacodemons in the Core’s nightmarish mythology.
Remember the third precept of the Jedi Code: There is no passion, there is serenity. Stay true to the discipline of self-control, and keep in mind that you are but an agent of the Force. Once you accept that grief, shame, revenge, and all other emotions that center on the self have no hold on you, you will emerge victorious. If you do not, you will emerge broken and screaming. You should hope you do not fail the Trial of Spirit.
“During the Trial of Spirit, Jedi must mentally face their deepest fears.”
This Trial would probably be the most difficult and intensive. It could be useful if done before the Trial of Courage however, as it will likely present many fears and insecurities. This Trial is the primary reason I think the Trials should be given more adequate time then just a few hours. I believe for this Trial, a student should sit down with a Jedi and go through their life, slowly, bit by bit.
About a year ago, I started typing up a sort of autobiography. It is amazing how emotionally trying this is, not to mention liberating. To go through all the painful moments, many that you forgot, to find the root of most of your fears and insecurities, and to examine the experience of your youth through an older, more aware and knowledgeable set of eyes. There will likely be tears and laughter, but in the end, the student would come out of it with a better understanding of themselves.
Ideally, this should be done with someone who has trained in a field like psychology, or specializes in this sort of healing, that way they can help the student deal with things, or know well enough to advise them to seek out additional help if needed. The student should also be prepared to take time to recover from the experience after if possible. This could be done in one day, or several days, depending on the amount of detail brought out and whether there were any major issues in a students past.