One thing to consider is that while you might know what you want to do, you might not be in the best place to achieve that.

I changed schools twice on the way to my graduate degree -- was miserable at my first school (but I learned a lot, so it wasn't a complete waste), then followed DH for geographical reasons to a school that could only offer me a second bachelor's degree, then moved again for DH's career to Seattle, where the department was a MUCH better fit for me.

A few people along the way tried to convince me that I might consider changing directions. The were only partially right.

Be true to yourself, and surround yourself with a strong support network!