Everyone has ups and downs when it comes to productivity. I'd bet that there are times where you perform way above and beyond. That balances it at the very least (you may even be above and beyond after the balance!)
Make sure how you feel is not how NT's want you to feel. Many NT's -- and I mean many -- will make you feel bad to make themselves feel better. If they are sensing you are down, many will try to feed off that so they don't feel so down themselves. It's the illogical emotion that makes people who have broken their leg happier if someone else breaks theirs too. They should feel worse because now TWO people have broken legs.
If you're not feeling down, many will actually criticize you to get you there too -- watch out for that! Aspies don't do such things because they aren't connected to the energies of others. How do they feed off of the negative energies then (or positive ones, for that matter, which makes aspies frustrating to leaders sometimes because they just won't get "excited" and "pumped up" by their persuasion and perception management, making leaders think they have bad attitudes when they are just fine). Aspies find strength and happiness from within and often wonder why the world seems to be out to make them feel bad. Imagine the advantage you have! Nobody has power over you. With that knowledge, you can make yourself the happiest person on Earth.