dropping a year for coaching NDA

You cannot always drop a year and try your luck in NDA. Either be sure on your preparation and motive or just think of any other stream/field.

One-2 year can be explained or justified but not more than that till the time you are very sure of getting in this field only.

If you are unable to study by self go with professional guidance but donot take your routine and study plan lightly. Everything matters.
So think upon what your interest is and which field you want to make your career in?