We being a capsule of body mind and soul need to balance body as well as mind. Sometimes, change in breathing pattern can change the mental attitude like if you extend the exhalation time, you will feel relaxed even during exams, interview, work pressure, etc and after you feel relaxed by changing or tuning your breathing and then you can use mental faculties to retain that calm and relaxation. I am saying so because some times what happens during anxiety or tension period, we do not have hold on our mind, at that time, we can use our breath to hold little bit on our emotions and then use our mental faculty to stabilize our emotions. Some times our body being in fatigue is not in a position to do some tasks, at that time, we use our mental power or emotions to do those jobs and after the body is started to run, we can use the body to retain that activity. In this way, we need to use the balance of our body as well as mind, both. We cannot deny any single component.
In view of the above, I suggest you to go for relaxation techniques - yoga nidra, progressive relaxation, etc. as well a pranayama - kapalbhati (not to overstrain), naadishuddhi pranayama as well as some asanas or little physical activity to achieve endodrine balance which are responsible for our mental stability.
To achieve emotional stability, yoga emphasize on purification on body and mind. The body is purified by shatkarmas as well as diet and mind by yama and niyama. Pratyahara, Dharana and dhyana helps in increasing concentration and purification of the mind as well as train it.