My first piece advice to prospective grad students would be to find a lab or an advisor that you mesh well with and are excited about working with. If you are on the same page and feel comfortable from the start, it makes all the difference. After that, trust yourself and your abilities! You are capable of more than you think.
My advice to any prospective grad student is to not rush into graduate school without some self-reflection about your passions, what you love doing and what you would like to study. This is because grad school can be a challenging place but also incredibly rewarding as it teaches you how to read critically, learn systemically, and think deeply. As such, I invite potential students to engage in some introspection and self-reflection about your motivations, desires, and commitments as this is a weird (but wonderful) experience distinctive from both undergrad and from other jobs so its important to not rush into anything without thinking.
Explore as many different topics and opportunities as you can, talk to lots of different people (who are interested in the same things, and different things!), and don't be afraid to ask for help to find the resources and supports that will help you succeed in what you want to do. When you're choosing an advisor, make sure that they will be able to provide you with the support and mentorship that you want and need, and that you are on the same page about academic and work expectations.
Choose a supervisor who makes you excited about your project. There will be times when your project does not go as planned and reminders of that enthusiasm and why you are doing the work are crucial to continuing through the hurtles.
I found being in a graduate university environment to be very beneficial for having access to experts on many topics. I would encourage new graduate students to not be afraid to reach out to various professors and other graduate students that can help guide you and offer advice.
My advice would be that a Masters degree is like a roller coaster. You will have your ups and downs in your research but that is all apart of being a scientist! There is no such thing as a 'bad' discovery.
Pursue research that you truly believe has the potential to improve life. Knowing you are working toward something more than just a degree can help you find the drive to make it through the difficult or dry aspects of your time in graduate studies.
Your time in graduate studies will provide many opportunities, but don't lose touch with yourself. Take the time to do what you need to in order to maintain your sense of purpose and direction, then live out of that. Don't be afraid to try new things, but remember that no one can do everything. Be selective.