I say to me that I don´t have to test so much manually and concentrade on important things. So I write tests, see what my past I done. Make that pretty and the best thing I feel good :)

A good test suite is the quickest way to ensure that you write code that works. There's no need to trick yourself into doing something that makes your job easier!

Set up a test coverage tool. Be mindful of focusing entirely on the number, though. One good test case is worth more than ten that have no assertions.

We can always test the happy path of a feature. But, testing negative cases is painful. Especially, when you deal with lots of data to be input to deal with.

I say to myself, "Dude, you cant test all of them directly. Better write one test and copy paste it over!". It always works :D

It's more easy if you think in a TDD way, and make tests BEFORE coding

Make a big project without tests. Imagine the client requests changes. Now you wish you made those darn tests :)

I have a note written on my desk which says :

I will find you and kill you - Your boss

So, I always see this and think if there's a bug in production my boss is gonna kill me. ;)