Antisthenes used to say that envious people were devoured by their own disposition, just as iron is by rust. Envy of others comes from comparing what they have with what the envious person has, rather than the envious person realising they have more than what they could have and certainly more than some others and being grateful. It is really just an inability to get a correct perspective on their lives.

One original thought is worth a thousand mindless quotings

It takes a wise man to discover a wise man.

I like best the wine drunk at the cost of others.

Nothing can be produced out of nothing.

You will become a teacher of yourself when for the same things that you blame others, you also blame yourself.

He has the most who is most content with the least.