When people begin a new way of eating, they often look to 'substitute' for foods they used to eat that may have been less than ideal. For example, a person might 'substitute' a bowl of oatmeal for the danish they used to eat in the morning. The 'substitute' is supposed to be an improvement on the usual item consumed.
Here's why I don't like the term 'substitute.' It somehow implies to me that what you're eating is merely standing in for what you WANT to eat. You are will to accept something other than what you really want for whatever reason (typically because the new food is in some way a better fit with your new style of eating) but by calling it a 'substitute' you are implicitly acknowledging that item's second class status in your mind.
I don't look at cauliflower puree as a 'substitute' for mashed potatoes. I look at it as a delicious, healthy side dish. It irks me a little to see people call them 'mock mashed potatoes' and then hear people bitch and whine about how cauliflower doesn't taste as good, doesn't have the right texture, etc. IT'S CAULIFLOWER. A yummy and highly nutritious vegetable in it's own right. One should accept it for what it is, rather than blaming it for what it can't be.
My theory is that the internal monologue you have about what you're eating influences your psychological satisfaction. If you are always saying to yourself "I want x, but I'll accept y" it is unlikely you will be able to appreciate y for all it's wonderful qualities. Instead, you'll be blaming y for not being x, and wishing you had x the whole time. What if you said 'I am going to try y this time.' No reference to x at all. Then you wouldn't define y in terms of x, but as a freestanding entity. Perhaps you might be better able to discern and appreciate all the wonderful qualities of y you wouldn't notice if you were focused on it's deficiencies vis-a-vis x.
Why does it matter? Because if you always treat your new food choices as lacking in some important way, like how they taste, you will never fully accept and integrate them. You may continue to make yourself eat them, but you will feel deprived and unhappy. But if you make the conscious decision to take the new foods as they come, and give them a fair shot in the taste department, you may in fact find that something you thought you wouldn't care for is actually pretty darn good.
I firmly believe that the way you frame a change in eating psychologically has a huge effect on whether you can make the change effectively. I don't use the word 'substitute' for any of the foods I eat. For example, I don't 'substitute' coconut milk for cow's milk. I use coconut milk instead of cow's milk because I know that coconut milk has significant benefits for me and it tastes really good. I don't 'substitute' spaghetti squash for pasta, I view pasta as a nutritionally deficient in comparison to spaghetti squash.
I know it may seem like a small point, but I think it's an important one. Little syntactical choices have been shown time and time again to reflect the overarching mentality of a person. At the very least, it is something to ponder.