What are stop quick remedies for jaw/teeth clenching?

A few options!!: Clenching is a behavior which is most often subconscious rather than deliberate; this makes stopping clenching a difficult task. Relaxation therapy and hypnosis have provided some success. Another common option is the use of an oral orthotic (mouthguard). Consult a psychologist or an orofacial pain dentist.

No quick fix: Clenching occurs during the day, grinding of the teeth at night. There are many variables involved with clenching and by becoming aware of it often causes one to clench more. A daytime splint (mouthpiece) can help, but i would recommend a custom one, not an otc mouthpiece. You really should be evaluated to determine the best options, with a thorough history and an exam.

Day vs night: Daytime habits can often be controlled voluntarily. "Teeth apart, lips together". Night time grinding cannot be controlled by volition. If stress/anxiety related. control this. You may need a splint made by your dentist. Bruxism can lead to TMJ problems.