You can't write everything by yourself - the missing link

I always tend to build software myself, not just coding, but also thinking about it, architecting it, experimenting with it and so on. It is always difficult to convince anyone in this approach compared to an off-the-shelf product reuse. Whenever such an argument comes up, I often hear this - "Well, you can't write everything by yourself, you have to use product X !" Indeed, it is impossible to rewrite an OS or a database engine, or a programming language, you have to reuse an existing piece of software. Not that I believe in a developer with a golden keyboard who writes infallible code (in Redmond, Bangalore or anywhere else) but doing so is just very impractical. Moreover, the truth is - you really can reuse just about anything, and doing so often gives good results. I never knew an answer to this, until now. I suddenly understood that it is this:

Even if you haven't written it yourself, you ought to know it so deep, as though you have.

The typical approach contradicts to this, you install something and just assume that it does what you need, exactly the way you need, that it will save you from all the problems you might possibly have. This is a mistake, a very convenient illusion. More often than not, it results in products being used in the wrong way, performing terribly, breaking on you, being cursed and thrown away only to be replaced with another of the same kind, only more expensive and fashionable.

It is therefore crucial to understand the working principles of the software that you reuse, to know the internals, what kind of problems to expect, and so on. And then, will you excuse me for repeating myself, but doing a lot of development on your own helps enormously in understanding the software written by somebody else.