I find this a problem common among beginners. If I give you code, you can understand the process and what the code does. But if I tell you to write a brand new code from scratch, you are stuck right from the beginning. Did I run into this when I first started? I don't remember. But I see this all the time.
The era of the Internet today makes it easy to copy and download code snippets, which encourages lazy thinking. You see this all the time on blogs. People would comment "Code doesn't work! HELP! HOW DO I FIX!?!?". And this is coming from using a simple code how to convert a file to a string object, for example. I'm not pointing out that the code doesn't work, but I'm pointing out the sheer laziness in people that they expect things to fall on their lap and work. When things not operating the way they expected, they don't bother to find the solution themselves.
It only comes from experience, and it has to be the right experience. Always write code from scratch. It's okay to look at code from web, but only as a reference, not meant to be copied directly to your code. 90% of the time that code won't be compatible to your code anyway. Never, ever, copy-paste and use code you get from web, conferences, CDs, or anywhere else. It's okay to use prepackaged libraries (like STL, SDL, Ogre, 3rd party libraries), the ones that you don't have to look at their code to use it.
How can a writer be a writer, if all he does is copy someone else's work? Programming the same way.
That's a main problem of mine.
For example, the Tic Tac Toe game, I keep trying to do it the exact way that the other guy does it, and I get stuck, and constantly refer back to his code to see what I am doing wrong. Not to mention whenever I try doing it by myself, I constantly think about that persons code. So I can never try it myself.