When I design websites, I like creating many different versions of the same sections. I simply duplicate the section, make some changes, duplicate it again, and make more changes, etc. I want to find that one design I love and then I make it perfect.
Sometimes you may have an idea that you need to quickly visualize it and then show it to your coworkers. I often grab a screenshot of an existing page and modify it in Photoshop or Sketch and have a quick mockup ready.
Your time is money, so being able to quickly produce many iterations is very important. Speed matters. You can always polish it later.
You don’t need to master the design software you use. All you need is to learn the basics, but you have to learn how to use them really, really fast. Create shortcuts for the most useful features and practice using them until it becomes as natural as typing on a keyboard.