End of my extravertism

I suppose that the theory of MBTI remaining the same for one's life isn't false. A few days ago, I thought that I had a sudden change in MBTI (Wow!), due to me being too high due to orientation. Just one week later, I am back to my old, introverted self again. Well, today was my classmates birthday and I didn't really wish her a happy birthday. (Or at least do a proper one despite not knowing o.O) Neither did I do that last year on a male classmates birthday, proving that my unwillingness to do so wasn't due to the slight gynophobia which I have. Instead, it is just something which I don't do. Maybe I should disclose a fact to no one here (please understand the deeper meaning of this diction), I'm an extreme I, N, T and a borderline J. It's just that I was trying hard to use my E during orientation that made me seem a little less anti-social. When the orientation ends, I continue my search for true friends.