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.
Remember that research never goes as planned and to not let failed experiments or unwanted results keep you from working hard on your degree. No one gets through graduate school without failed experiments and huge changes in their project plans.
There are so many ways to pursue your passions and interests. I'd recommend that prospective grad students be certain that they are ready for the rigour and commitment required by graduate studies. Be open to new ideas, critiques, and other ways of seeing the world. Learn from your peers, students, university staff, and the wider community, in addition to your professors. Be generous with others and build community. Don't forget where you come from.
Networking is essential when considering graduate studies. I met my research advisor at an informal chemistry meet-up in Brass Taps two years prior to working for him. You'll never know when opportunities present themselves, so it's important to take chances and meet everyone you can.
Find what interests you. Many other grad students are much younger than I am and will be entering a life's career following completion of their studies. Looking back, I think it's important to pursue your passion and let the career, money, etc., come from that. During studies, stay on top of things. At the same time, don't neglect other outlets, pursuits, interests: things have a way of connecting in unexpected ways.
I loved being a PhD student here. My advisors and labmates were all very supportive of my research endeavors. I enjoyed being in charge of my own research project.