If you want to do more push-ups, you have to do more push-ups.
As for books, Practical Chess Analysis by Mark Buckley. To start, you have to know the board. Is e6 white or black? Does a bishop on b2 attack h7 or g7? How many moves does it take a knight on f3 to attack g7? You have to know the answers to these questions instantly without thinking.
I have a serious problem calculating throughout the game. Does anyone have a solution to making improvement with this? I already understand that Tactics training helps with this. Can anyone suggest tools or other training techniques to make a substantial improvement on this? Thank you very much for any feedback. Perhaps a particular book that specializes in this?