This is the best way to improve your interviewing skills. Make sure both of these tasks get completed after an interview. They are critically important to obtaining the job. Failure to send an appropriate thank you letter could result in the person who did send one getting the job. And if you don't evaluate your performance on the last interview, you will be unlikely to improve your future interviews.
Nobody likes being analyzed and evaluated.
Most people become nervous at the thought of interviewing, and that's normal. However, there are a number of steps you can take to become better at interviewing. Most of those steps involve preparation and practice. You can increase your confidence by identifying your goals, preparing appropriate questions to ask, and anticipating as well as practicing difficult questions. Your increased confidence will make you a more effective communicator.