That makes sense and accords with one of the most common perspectives I've been running across from people who favor the idea of Buddhist prayer. Generally, they say that the buddhas, bodhisattvas, and some deities serve as a kind of cosmic source for all the positive, compassionate, wish-fulfilling potential of the Universe for all sentient beings, but many beings are unable to benefit from most of this powerful goodness because their karma prevents it. In that regard, I could see things like prayer, mantras, meditations, and even rituals like creating a sand mandala as being methods for purifying oneself of the negative karma and focusing the mind into a more compassionate state that would make one more capable of benefiting from the pure goodness that these sources are capable of generating. That idea makes a lot of sense to me.
It just leaves me wondering if it's considered acceptable to pray to, for instance, Tara with a specific aim in mind. To use an example from my life, my dog, who's pretty much been my best-friend for the past 12 years died the other day and I've been pretty depressed about that because I would do almost anything to help him. Of course, now that he's gone, there doesn't seem to be a whole lot left I could do for him. It makes me wonder if there's any merit to the idea of praying that he be comforted now and guided by Tara or any other being potentially capable of this towards whatever next incarnation would be best for him. I mean, that isn't the only reason why I'm thinking about this. I've often pondered the concept of Buddhist prayer in the past, but this experience has really renewed my interest in the subject in a much more significant and personal way because, without prayer or some other direct method of trying to help him, there doesn't seem to be a whole lot I could do other than sitting around feeling kind of depressed and powerless.