While it is nice to receive and give constructive criticism (when the time is right), it is not nice when such criticism is given at all and every opportunity. If you or your partner is overly critical of the other one, that could spell disaster for the future of your relationship. This is one of those things that can start pretty insidiously in the beginning part of a relationship, but that can slowly grow into a complete monster at the latter parts.
You need to very carefully choose quality over quantity when it comes to giving criticism to your partner, and to other people in your life (this is especially important when it is about your coworkers at the office). The more you improve in this area of your relationship, the better things are going to become for the both of you.