In his highly informative book A World Full of Gods: An Inquiry into Polytheism, John Michael Greer mentions an intriguing concept: that of the Shinto kokoro no kami, or a "heart-god"... that is to say, a God or Goddess of the Heart. According to the section, the idea has parallels in ancient Roman worship as well, and has connections to the possibility of having a patron God or Goddess.
It seems to me that a fulltrui or fulltrua need not necessarily be the same as a "heart-god." I suspect that there is room for variation and that the terms do not always have to describe similar relationships. Here, though, I can only speak to my own experience: my fulltrui Forseti has been my "heart-god" since I started walking with Him.
In this post, I'll attempt to share a few of my own experiences of relating to a Divinity in this way. As with any other way of connecting with our Gods and Goddesses, it may or may not resonate with the experiences of others.
I have mentioned before that Loki was the first Norse God who approached me in what was then a recognizable form. He soon introduced me to Odin, and within the space of a few weeks, my former, general spiritual Panentheism was abruptly replaced by what some term "hard" Polytheism. No one introduced me to Forseti. I was doing my own reading, and I sought Him out by myself. At the time, I was not sure if I could expect much of a response. I was beginning to form a misty impression that He had a great deal to do with lawgiving, but the records on Him were scarce, and the ones I found most inspiring presupposed that He was the same Deity as Fosite, a specifically Frisian God.
Forseti's presence was not as nearly strong as Loki's in the beginning, but what I could sense distantly in meditations drew me in. The feel of Him was subtle, but somehow kept tugging at me in ways that did not fit easily into words. He seemed reserved, but also curious. Later on, I did get a sense of Him in something roughly comparable to the more immediate way that I sometimes felt Loki or Odin. I was at work on a busy shift, rather drained by the sheer volume of cases that evening. There was a lull, and a brief but uplifting sense of white light and warm comfort washed over me. I knew it was Him.
When I took my oaths to the Norse Gods, I was already instinctively hailing Forseti as the "God of my Heart," though I had not come into anything so formal as a fulltrui relationship with Him as of yet. That was to be a decision made a somewhat later, after spending more time with both Him and Loki and connecting with other Deities in our pantheon. In another sense, though, long before I consciously chose Forseti, the decision felt like it had already been made. Some part of me seemed to know and always seemed to have known that this is my God.
In my own experience, "heart-gods" can bring with Them the profoundest sense of friendship. To be very frank, I first felt this most with Loki. There was a feel about our Trickster of a confidant, of someone with whom I could share any thought or impression, any experience, story, or escapade. Think of that childhood best friend you always longed to have and multiply that exponentially: such may be one aspect of a "heart-god" relationship. It's been a slower and different path with the Divinity who turned out to be my fulltrui, but the sense of friendship has developed in its own way, with its own depth, and I would not trade it for anything.
This is not to say the a God or Goddess of the Heart cannot also be... entirely a God or Goddess. A heart-friendship with a Divinity can be wonderful beyond all words, but our Norse Gods also challenge us in ways that we cannot begin to predict, inspiring us towards growth and greater heights of self-honesty, responsibility, and inner vulnerability than we may have ever known.
The heart gives life, but it is always working. It does not get to take a break and stop beating for an evening. And that can be another side of having a "heart-god." You never cease belonging to that Deity. You can't "take the night off," slip away, and act out in ways that are anathema to your God. Fortunately, They are very wise and very patient, and They do take the time to guide us into the heights of what we might be. But it is not always an easy walk, especially when we have been taught by the surrounding culture to view ourselves as perpetual "seekers" with perpetual choices. Finding can bring real commitments. The heart is the life and center of a being; a "heart-god" becomes the life and center of His or Her devotee's being.