I have found the best way to understand anything, is with the law of analogy found in the Hermetic principles. The I is represented by the Solar principle, the Sun. Which is a manifestation of the Fire element. The properties of Fire are Light, Heat and Expansion. Take note of expansion, we are forever expanding because of ego, all of us in some way want to be a little bit more than what we are right now, whether it is be better looking, healthier, more money, more knowledge, more spiritual power or whatever.
Then of course, there are two sides to everything in the existence, there are negative manifestations of this same property of the Fire element, such as jealousy and envy. I say negative, not in a moralistic sense, but in terms of the duality, there is a positive and negative side to everything.
Envy is the polar opposite of the same desire to be more than you are, - feeling like you aren't as good as you would like to be / someone else. You should never condemn or judge yourself for any of your emotions, they should always be able to find a healthy outlet.
That being said, all negative manifestations of the elements, can be balanced by the opposite elements positive attributes. For instance a negative of the fire element, such as envy can be counter balanced with the humility which the water element can bring. Conversely the negative, sluggishness the water element can bring is offset by the desire and wanting to expand of the Fire element. It is all like a clockwork.
The enemy likes to emphasize these negative manifestations to condmen people and create confusion, believing that the sense of self, the I and the desire for expansion is bad. When in fact, it is just the same as anything else in the physical plane, duality. A positive and negative side to everything. We need the I and ego in order to expand but of course like anything else in life, there are negative manifestations of this, we are made up of four elements, an electric and magnetic fluid, everything is dual, with the right knowledge we learn how to counter these negative manifestations.
I only call jealousy negative because it feels unpleasant, it's a kind of hurt to feel less than another. I do NOT mean that you are bad for being jealous or should attempt to repress it. Just to be 100% clear on that. A slight misunderstanding of these type of teaches can cause a lot of problems.