Hello Aniket,

If You participate in Josaa 2019 and if you didnot take any college (that means you didnot accept the seat letter and freeze the seat that you have booked), then you are eligible to reappear in the next year JEE Mains and JEE Advance . 

But from my opinion if you have decided to prepare again for the exams then I recommend you not to sit in the counselling , be determined , put some efforts ,crack the exams next year and then take the college of your choice.

Wish you all the best !!