I'm on a tight deadline and finding it harder and harder to write good, DRY, SOLID, code. It's becoming more enticing to copy/paste chunks of code to make slight variations to it's behavior as design time goes up. It's also taking a long time to get back into the code base whenever I have to do a context switch (From one project then back to this one), I have a feeling of dread whenever I go back to work on this project.
What steps can I take to remedy this? The extra time it might take needs to be justifiable as well, my boss is not a developer and is not familiar with development or software life cycles so explaining might be more difficult than normal.