I didn't learn MBTI until I was 42. By that time, I already had my own way of dealing with people, my own persona that I brought to the table, my own message to deliver, and my own ways of taking charge of a situation. Before learning MBTI I already knew from experience that various people might react to me and my message in some odd ways; but that was no reason to change me or my message. Overall I just figured "people are people" and didn't worry too much about their reactions.
Things haven't changed much since I learned MBTI. For most people and situations, I just bring the same old "me" to the table as always. After all, I'm Fi, not Fe; I don't feel the need to "manage" the reactions of other people in a normal conversation. (Since I'm Fi, I tend to take it for granted that the universe revolves around me and my reactions; it's up to the other guy to keep me happy. )
With me, MBTI comes to the forefront mainly at times of conflict or stress. If the wife and I are in a weird mood and nitpicking at each other, or if I'm in a meeting and my boss and co-workers are at each other's throats, then I quickly inventory everyone's MBTI types and remind myself how they handle stress so that I can get a handle on the dynamic and manage the situation if that's necessary. Or if I'm telling someone an important message and they don't seem to be getting what I'm saying, then I'll stop for a second and think about whether my message needs to be crafted better for their personality type. And of course, I use MBTI to manage my own reactions under stress; in many ways self-knowledge was the single biggest thing I gained from learning about MBTI.
It's true that in the company of a couple important people or easily identifiable types, I may adjust to those people on a regular basis and mirror their type somewhat. But I used to do that kind of thing even before I knew MBTI: Around the intellectuals I acted like an intellectual, and around the partiers I partied.
Overall, learning MBTI didn't change how I interact with people on a routine (social) basis. [Edit:] But I do keep MBTI close at my side and routinely analyze social dynamics through the MBTI framework when the dynamics get a little strange and need analysis.