Just need an advice from you all (serious)

I just gave my maths exam and I barely think I'll make it past 75 criteria. Not that I'm getting IIT/NITs anyways but still when I think of it, it sucks. What's the point of doing engineering then when I'm not even good at the subjects. What will i make out of my mediocrity? When my parents ask if I want to try law, I think to myself what if I feel the same things with that field. What if people ask my about my 12th marks and all I'd come up with is 60%...I'm such an embarrassment.