It's ok to stress; only for a moment. But not stay there. Whether you choose to be angry, upset, annoyed, take a nice deep breath, INHALE deeply then EXHALE deeply. Take your time and slow down for the moment, feel you body at ease and be still. Know you are safe and about to feel better in a moment. Give yourself time to register exactly what you are feeling. For example, "I am really angry and hurt....(my boyfriend no-showed me at the library)." Before we start creating our own story of why your boyfriend, or the person meeting you, no-showed you, we need to take a step back and realize there can be 100 different reasons, but only one is the true answer. We have no control over other people's behavior or their problems, but we do have control over how we behave when difficulties, problems or miscommunication arises. It is always best to have clear and open communication when you are making appointments or expectations. Practice inner peace, patience, kindness and non-judgment as a daily practice, so you can better manage yourself when inconveniences happen. Communicate first, then express your honesty and authenticity that the situation hurt and/or upset you; then work towards resolving situation and build mutual respect and accommodation, trusting that this will not repeat itself. Otherwise, you will examine if the relationship and situation is serving you and your mission in life.
Meanwhile, while in the process of examining the relationship, there are healthy natural approaches to rejuvenate and recover your body and mind in good timing: