Let us discuss the diet.
It is a concept greater and more important than what most people think, on many levels. Few people know that your intelligence can rise simply from a diet change, or that it can impose mental instabilities upon a person. Few also look at the term outside this material concept. What mental diet do you have? Your body and life can produce an outcome solely based on what goes into it. You cannot become capable of achieving your dreams unless you give the right fuel to the fire. A locomotive shall not run on water and you shall not run on crap.
Foods contain many nutrients, which are important to assess and work out what you need for your physical goings-on, but food has other properties that one takes in. Modern science often ignores such ideas, but not the countless religions of old. Food has material and spiritual properties, and can improve your physicality (mental and physical) and your spirit simultaneously.
This is not the time or place to dive into the depths of the world of nutrition. It is to be said, however, that one must assess one’s needs first and foremost; the sumo wrestler cannot expect to have the same needs as the bookworm, who again cannot expect to have the same needs as the long-distance runner. Do you run on diesel, petrol, hydrogen or ethanol? In regards to that metaphor, if some people are keen to take the ethanol part too literally, let us say that in regard to all illicit substances, careful assessment should be made into their use and the proportions and quantities one is capable of sustaining and needing.
Also look at the spiritual properties of your food. Your actions echo into eternity, and are destined to get lost in the chaos of melodies of existence. However, chaos is not as random as many would say; it has some purpose, albeit chaotic. Every action has a destiny, the fates can read upon this, and by making your actions, purposes, and intent pure to your inner ideals and ethos, it will echo in a way that befits your remembrance, and will have a subsequent effect upon the world, suiting the change you want. If eating animals does not befit your ethical principles, then do not eat them. Trust me, after a few weeks not eating meat, your body’s addictions to the animals will soon wear off until you do not crave them in the slightest. You just need perseverance.
I personally, however, see little means of differentiating between an animal that is alive or a plant that is alive. The only difference exists within the customs of society, not within the bounds of logic.
Maybe your spiritual nature lies in how you treat the animals you slaughter to eat, maybe you wish to bless them, or to release the remains of their spirit from the flesh-ridden tomb. There are many different customs within the masses of societies that have existed. Asses what YOU want, and then be loyal to this inner vision of purity.
The mental diet. It has been noted from times dating all the way back to Herodotus, that what is right is highly dependent upon the society and customs that one grows up within and comes to understand; it is relative to one’s situation, as subjective as the individual's perspective within his life, not forgetting his perception from that perspective, which will likely depend upon both his physical attributes at the time, AND his mental diet up to that point in time. Luckily there are points in our lives where our lifestyle changes, and our mental constructs no longer fit succinctly with what they think to be the right existence, and a time of inner reflection follows where layers are stripped back and a sculpture is carved from the ashes of your last construct. Likely you will change very little, but fine analysis can lead the better sculptor to look in greater detail, and to make his sculpture all that more perfect, aligning its form with the passageway it wishes to pass through. The smoother the bullet, the further along the musket barrel it will travel.
If one wants to become a good writer, then one should fill his mind with works of literature he wishes to emulate in style; if one wishes to be an athlete, he should study and assess the corpus of sports science; if one wishes to be a train driver, he should fill his head with the manuals of trains.
The people diet. If one wishes to be a martial artist, socialize with martial artists.