It depends on the obstacle. Fear is associated with what is called a flight or fight response. You can choose to fight or flight. Your body changes physiologically to prepare you for such situations. We as humans have an innate ability to defend ourselves in unforseen circumstances. We have to trust our instincts and our judgement. The best response to a gruesome spectacle would be to run away from the stimulus. This means that your entire body has to be in line with a response that is towards one ultimatum - run away from harms way. Somehow, we are able to overcome the most difficult circumstances that may cost us our lives. And we do not know how. We just have to beleive we have what it takes to respond.
In the meantime, its best to avoid such situations. However, for the daily griddle at your job; thats a different story. Along with your relationships and other normal situations that occur as part of our daily life. Those we should not try to avoid. We become stronger by dealing with obstacles so we are better equipped to handle future situations. Its a win win.
However, we should choose our battles wisely as all battles are not worth the effort. Some may cost you your relationships and those whom you love. We should exercise due caution and never react in the heat of the moment. Exercise some logical sense and restraint.
Have an internal dialogue within yourself so that you compose and filter your frustration or anger. Raw energy never yields satisfactory outcomes. Even if you are a boxer. You still need to know your stamina and your endurance against the opponent. Great question.