Hello Aspirant,

Now you can't cancel your application of JE-Main 2021 as now the application/correction window is closed  so if you are able to appear then it is recommended that one should appear for JEE-Main if got registered because you don't know how the paper is going to come, it might be much easier even beyond your expectations so if you appear you can get the advantage of it and who knows you might get good NITs on such score and if you don't appear then definitely you will not have any chance to get into top colleges like NITs/IIITs and suppose if paper comes harder than your expectations then also it will give you some experience and will make you familiar with your mistakes from which you can learn and can appear with much better preparation in upcoming attempts.

I hope this information helps you.

Good Luck!!