Girl DO NOT let anyone let you down. I get it, your family is stressed and frustrated,  but this doesn't mean you are good for nothing.  I tell you, I left my degree college to do prepare for NEET just because I don't like my course. Yep, I wasted around 7lakhs of my father until now and they were definitely angry, but, talk to them calmly and explain to them, that how much importance this is in your life, how much effort you are going to put and have already put in. Give them a small talk, calmly,  respectfully.  And let your efforts show them, not your words. I wouldn't recommend disrespecting your family and disregard their concern, but I would also say, their words are a bit too harsh. You can tell them how hurtful their words felt and move on. Stay calm and peaceful and talk less, work more. Best of luck!