While I agree with Casey, for some situations it's hard to do. You can't really develop web app in C# and Java in a simple way. Not only you have to fight the language design, but all framework and libraries are written with OOP, clean code and design patterns in mind.

So you might write your code in a straight way, careful to not lose efficiency and then you are going to call slow code.

So his advices are easier to follow on some scenarios than others.