Mistakes are necessary and unavoidable if you want to do something new and interesting. If you don't make mistakes during your PhD, it means you aren't pushing hard enough and taking enough risks; you're just doing what you already know.
But many PhD students are afraid of making mistakes
This is, in part, because the education system has trained you to avoid mistakes. For years, you had to learn the syllabus and reproduce it in an exam. Mistakes lost marks and marks determined how you ranked against your peers.
But as a PhD student, you have to drop this way of thinking. Mistakes are opportunities to learn and adapt and develop your skills. To avoid making mistakes is to deny yourself such opportunities.
This doesn't mean you should be reckless, but that you should give yourself room for mistakes in your project planning. This means testing your methods on a small scale and giving yourself the chance to find and fix mistakes early.