My worst sin.....

I don't do unit tests...

In my head I think its a waste of time..

I test the program myself, it works, why should I write another program to test my program..?

Unit tests are good. They are all just excuses cos I'm lazy

Dude, you don't write tests for now. You write them for the future for when you want to change something without breaking shit. It will also make it easier for others to understand and change your code, and it will force you to write cleaner, testable code.