The term gan in Japanese can be translated as "vow" or as "prayer". In any case it is about intention. However, there is an aspect to the notion of vow that is impersonal. A vow, in the Buddhist sense, is not so much a personal effort as a realisation of one's given purpose in being alive. Often we are triggered into a realisation of this kind by encountering the faith that another person has just as Dharmakara was by the faith that Lokeshvararaja had in him. The great vow is not of our own making, but is simply other power operating in our life. By self power we set up short term goals that are only distantly related to this fundamental vow. As we have made lesser vows that prevent us from realising our great vow that, the great vow continues to elude us. However, at a deeper level the great vow is always functioning, like gravity, The great vow belongs to the universe. It is the real meaning of Buddha nature. It is "gan ga sa butsu" (=my vow become buddha). Buddha nature does not belong to you or I but it works through us and each time we surrender to it more completely we feel euphoric and full of faith because at that point we are freed from self power. Then we become capable of great effort because it is effortless effort, springing directly from the primordial source which is simply the real nature of our life.
["Gan ga sa butsu" is one line of the text "Life of no regret"]