Hi,
Welcome to icliniq.com.
From what you are describing, it appears that there is a personality disorder. It is not a disease, just a kind of personality that is not very adaptable. This also means that there is nothing to be ashamed of or worried about as far as the diagnosis is concerned. This is best treated with a psychotherapy program. Since you are not very keen on visiting a doctor, let me try to help you here. The first thing to do here is understanding yourself better, so that you know what to expect from yourselves. Everybody has mood changes in response to what is going on around them. But, in persons like you, the mood change tends to be greater both in intensity as well as duration. Associated with your mood change are other maladaptive behaviors. The lesson you need to learn here is that the next time when you have an intense emotion, either positive or negative, do not act immediately. Wait for an hour. Let the intense emotion pass. Distract yourself until then. You have to plan beforehand as how you will distract yourselves, because when the actual situation arises, you will be unable to think clearly. For example, an escape plan is to listen to a particular music album on your smartphone next time when an intense emotion gets triggered. It must be a common experience for you that once a particular event has passed you often regret what you might have done. Hence, the key thing is to not act impulsively in the heat of the moment. Though the temptation to act may be difficult to resist, this applies to situations where you feel like cutting yourselves also. The next thing to understand is that a lot of people have this kind of a problem, although it may not be evident to you up front. So, do not worry too much thinking that you are abnormal, which you are not. Learn to accept yourself, find your strength, focus on them and build on them. Take care.