Development and Debugging are the Same Thing
The sooner a defect is found, the easier it is to fix. If you remember nothing else from this article, remember that.
You'll find lots of articles that talk about the monetary costs of defects getting into production, and how they're more expensive than defects that are caught by QA, which in turn are more expensive than defects caught by an internal code review prior to QA, etc. This is all true, and the same concept holds true right down to your own hour-by-hour development practice.
Debug early and often. If you introduce a defect into your code and you notice it within minutes, you can probably locate and fix the offending code pretty quickly based on what you changed recently.
Not so if you write 200 lines of code and then try running your feature.
Debugging isn't the part that comes after you've written your code. Debugging is the process of writing your code. It's the iterative cycle of writing a bit of code, ensuring it behaves according to spec, writing a bit more, and so on.
There will always be bugs that get past you and into production. We will discuss strategies for finding and fixing those in a few days. But the first step that you should be taking right now to make your debugging easier is to do it more frequently.