This is a hugh, hugh question, and a full answer could fill books.
    For starters, we have to evaluate how unusual the degree of wear is for
your age.  We have to look at diet, whether you grind or clench your
teeth, what your bite is, whether you have missing teeth, whether
remaining teeth have drifted.
    If the wear is consistent with your age, no treatment may be necessary.
 If your wear is excessive for your age, treatment may range from some
protective device such as NTI or other nightguard, to full-mouth
reconstruction with provisional restorations to gradually regain your
degree of vertical opening.  There are many intermediate restorative
procedures that may be tried between or in combination with these extremes.
    You need to get to a good restorative dentist who can speak to you
about both your fears and your treatment goals.

Good luck!
Steve