sometimes future does not turns out how we want it to turn out, you can for sure do better the next time, don't lose hope, just be consistent with your studies and stay strict to your principles you will for sure score better marks.

what if I again score bad marks? because I didn't completed my syllabus?

are your exam near?

first of all..understand what you did wrong previously(it could be your way of looking at exam, your learning habits, solving previous yr question paper, your attitude on day of your exam and many more) and improve it. And then have this satisfaction that you did your best...you know we usually feel this inferiority after failing because we are defining ourselves with people's perspective...other than that we are capable of standing up again and giving our best again. But also you should know when to stop