If you're hyper fixated on getting 100% again, I could summarize everything you need to regain it
I will agree with what's already been said by Lew though, you haven't lost 'perfection' or any of the perks gotten by getting it, merely have a number less than 100% that you can work towards (or ignore, it won't change anything). 1.6 adds events and items that are really fun to explore for yourself for the first time, I had an absolute blast going through everything when the update first dropped and I assure you it'll be much more enjoyable an experience seeing everything for yourself instead of rushing to raise a now pretty arbitrary number.