My father is experiencing feeling anxious (worsened by: psychological stress) . the following also describe him: irritability and difficulty sleeping. what should he do?

Counseling.: Assuming there's nothing medical going on, for consideration of which he may want to visit his medical doctor, then a visit with a psychologist/therapist/counselor would be wise. He may need help with elucidating the cause of this anxiety and developing coping mechanisms.

Start w med eval.: It may uncover underlying medical problems that need to be addressed. Cognitive Behavioral therapy can be effective. Psych meds may be indicated. Aim for daily exercise, 8 hrs sleep /night & good nutrition w 5 servings of veggies & 4 of fruit per day. Try tai chi, yoga, Qi Gong, progressive muscle relaxation, deep breathing exercises or meditation. Take care.