title: Best practice in C++ - when should I divide my project into .h and .cpp files?
body: <p>I'm starting with a new project. 
  I know, that the idea of dividing a project into .h and .cpp is good, but it's pretty annoying for me when writing and testing the code.</p>
  
  <p>Is it a good practice to split my project into .h and .cpp while writing a new code?</p>
  
  <p>Or is it better to write whole classes in .h and then split it into .h and .cpp (when my project is finished or nearly finished)?</p>
  
  <p>Or should I write just new classes in .cpp files and then create individual .h files?</p>