Viswamutra tested and treated King Harichandra badly.
Muni Durvasa was famous for his anger.
Karna too suffered by the curses of Parasurama for lying .
The egoistic Muni Konkanava tried to show off his magical [pwers to Vasuki w/o Thiruvalluvar, and failed.
Sakuntala was cursed for her love by her own father Kaushika Muni.
No life without Sun
The epics do not give a judgement as to who or what are good. They give all kinds of occurrences and happenings and makes the people to ask questions who, what why, how etc and come to their own answers. But they give indirectly the eternal values to be followed by human and society.
But generally anger isn't good for health especially for mind.
As far as meditation is concerned I too have heard that meditation helps in controlling anger especially unjustified anger. Your question about rishi muni that why they vented anger despite doing meditation I see myself as a out of place creature, however, using common sense it can be conjectured that something was terribly wrong from either side otherwise how cursing could be imagined from people of meditation.
K Mohan @ Moga
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease
But also gets angry and this is because. Q once again did not act like he was thinking due to his own negligence. If we talk about anger in daily life, then many examples can be found.
An important reason for anger is stress, so the easiest way to calm it is to relax your muscles. Take deep breaths and be silent for two minutes, and in a while you will find that you are calming down.
Close your eyes and take a deep breath. Now think that stress is going away from you. As you think, you will find that stress is really going away from you and your mind is calm
Keep your Face to the SunShine
Patience and perseverance pays
As mentioned by author meditation or prayer may make us less prone to anger. So practising meditation to avoid anger is a good option. If no meditation the alternative is prayer. If you immerse yourselves in praying God, you may become calm and you will not get angry easily.
Sages are very calm and they have a lot of patience. Generally, they never curse people easily. But there will be a limit for their patience also. If somebody tries to irritate them beyond their threshold they will get angry and definitely they curse them. The cases we hear have happened when the saints are humiliated beyond their threshold. They have the capacity to curse and at the same time, they have the capability of giving boons to the people. So one should respect them always.