It is not easy, but this is
certainly an achievable goal, as long as you stick with it.
I carried around
this book with me everywhere I went my junior year, and was able to get up to speed quite quickly (ignore the 21 days thing). Look for the latest edition. The best thing I like about this book was the detailed code examples along the way.
Aside from that, the most important thing to do is to just code. Write code as much as you can. Get excited about it! If you have a mentor, ask questions (if not, ask here or other C++ forums). If you have anyone to learn with, do the same problems, compare answers and learn from each other. Reading a book or attending a class will only get you so far. Find some problems to do and try it. Write some code, learn from mistakes, experiment with it. There are plenty of programming problems and a lot that you can learn with just the basic tools (i.e. outside of using the robot, from just an IDE such as Code::Blocks).