Tsongkhapa's commentary states that bardo yoga relies on the yogi's previous practice of tummo, radiance, illusory body and dream yoga. After all, the experiences of illusory body and clear light in waking and in sleep states is similar to the experiences in the post-mortem bardo. Thus, when death comes, one applies the same principles one used to attain the yoga of radiance/clear light in sleep:Should death arrive before supreme enlightenment has been attained, and one wishes to apply the yoga for enlightenment at the time of death, then the death process sets in one engages the yogas of controlling the vital energies in order to recognize the clear light of the moment of death, using the same principles that were applied in the yoga of retaining the clear light of sleep. In this way one enters into the bardo experience, applies the techniques learned through the yoga of the illusory body of dreams, and generates the bardo body as the illusory body of the bardo.Thus, to achieve the clear light of death, one must go through the practice of tummo, the dissolution of the elements process and the visions leading up to clear light and so forth. One must have the ability to stabilize one's mind on an understanding of emptiness and the yogic means for unducing the four blisses to succeed.