I am a good player when I have a plan. If I have a certain goal in mind, I can see the way to it. But in quiet, planless, positions, I have difficulty as an attacking and tactical player. What is the best way to cope with them.
A good middlegame strategy book will help you figure out what sort of plans you can execute besides just attacking ones. I enthusiastically recommend Mastering Chess Strategy by Johan Hellsten, a very nice breakdown of all the standard strategic plans and tactics, with hundreds of problems to test your understanding.
It seems you are good in tactical calculations and you can find combinations well, but you lack in strategical moves.
I think, you should improve your middle-game skills. To achieve this, you can read middle-game books and analyse the games of GMs. For example, try to guess the next move in those games, after that try to understand why they played that move... .
On the other hand, there are many useful middle game tutorials and training sites on the Internet.