To be honest, I don't really know for sure yet. I already have a bachelor degree in Earth Science (geology and geophysics) but found out while writing my bachelor thesis that I liked physics and maths way more. Since a second bachelor degree in Holland is very expensive, I decided I'd move to Germany since it's pretty cheap there, I like the country and I already spoke a bit of German. Most of the stuff I did in my previous bachelor degree is not really useful for the stuff I do now, but I've learned a lot about what I want to do, about social stuff and studying in general.
So the only thing I know right know is that I'd like to work at a university. I love the combination of research and teaching. Therefore, I at least want to do a PhD in something maths/physics related after I finish my masters... but that's still a long way away, since I started my bachelor in maths last October.
Maths is even more useful though, depending on what area. I just enjoy anything that applies to the real world in a practical way.
For me, it's almost the exact opposite
I don't really care if the stuff I do is or will be applied in some way or not. I just enjoy doing all of the maths stuff, it makes me happy (and of course frustated at times when I don't get it). It's almost like puzzles for me.
Of course, most of the maths, even the most abstract stuff, is useful because it may be applied sometime in the future even though we don't have a use for it yet. I once read a quote, I don't know by whom, from a mathematician who was asked by a politican about why he thought his research should be funded. His answer: 'Someday in the future, the stuff I do now will be applied to something for which you can make the people pay taxes'.