This year will mark my 23rd "veganniversary", and also my 7th full calendar year of maintaining an entirely raw diet.

Over the course of time since having begun my transition into veganism in 1990, I have periodically chosen to alter my lifestyle in various ways for different reasons (which is essentially how I evolved to eliminate gluten, refined sugar, cooked, and acid forming foods from my diet). I am not actually a devotee of the lfrv ideology (especially not since having been injured rather severely), though for quite a long period of time I was largely adherent to an Ahimsa (entirely vegan, no roots, bulbs, mechanically harvested grains, and very few seeds/nuts or stalks), and grew around 90% of my own food whilst sourcing the remaining 10% or so directly from organic/veganic growers.
Essentially, I was mainly fruitarian for reasons relating to concern for other species, spiritual growth, and environmental concerns (as opposed to personal health or fitness goals). As a student of theology and Interfaith cleric I participate in numerous spiritual observances, which also affects my dietary intake rather dramatically at times.

Over time I have also learned how profoundly certain foods and dietary alterations can affect the body/mind/spirit and also one's ability to shift/transform/adapt to any/all new situations and circumstances. Long periods of fasting are generally quite common for me, and I would normally have transitioned into a full-on water fast for the entire 40 days had I simply less work to do in my garden and continuing to heal/rehabilitate my physical body during this time.

My decision to eliminate tree nuts at this time is partially due to my inclination toward returning to a largely Ahimsa lifestyle, though I have really only pledged to abstain from eating nuts (& roots/bulbs) for 40 days of Lenten fasting.
As I'm still healing/rehabilitating from an injury, working on a culinary book, instructing and distributing food on behalf of Lorax Community, a 40 day water fast was deemed unwise at this time by my nutritionists. As such, I've simply chosen a single group element of my daily food intake from which I could probably use a "time out" & spend time focusing on working with other things.
My decision is also somewhat related to a mild allergic reaction I have occasionally encountered when eating various tree nuts, which caused my gums to become very sensitive and painful (sometimes to the point where I felt as if my teeth would fall out). Although I have not experienced this to any severe degree since having become more educated about the cause of this reaction (too much L-Arginine) and subsequently given up cooked food, I actually did find myself dealing with it on a milder level two weeks or so ago. I immediately began supplementing my diet to fix the issue, but a total fast from tree nuts for awhile (followed by gradual reimplementation of the more alkaline varieties) back into the diet is really the best way to go.

Never fear, as certain nuts are likely to reappear in my life/repertoire just after Pesach.
 In fact, there's an enormous 3lbs of amazing macadamia goodness from Calimac Nut Company just waiting to be transformed into some new "cheese" recipes around that time... ;-)

So that's my rather lengthy personal reasoning for abstinence from tree nuts. I realise that my explanation is likely very different from any other one has received (or will likely receive in future), but I wanted to explain properly and sincerely hope that others may be able to find something useful within my epic explanation.