Complexity control is the central problem of writing software in the real world
A software system is transparent when you can look at it and immediately see what is going on. It is simple when what is going on is uncomplicated enough for a human brain to reason about all the potential cases without strain
If you have the right attitude, interesting problems will find you.
Good programmers know what to write. Great ones know what to rewrite (and reuse)
A security system is only as secure as its secret. Beware of pseudo-secrets.
When writing gateway software of any kind, take pains to disturb the data stream as little as possible - and never throw away information unless the recipient forces you to!