Depends on the cause, and how serious the cause is.
If the cause is something I understand, and it’s not serious, I just find myself unwilling to talk. Then I’m back to normal, very quickly. And if it’s serious, I will need more time alone, and sometime I’m unable to do anything. Sometimes the sadness can last for days.
If the cause is something I can’t understand and serious, I will experience the five states of grief. Firstly I will play the event repeatedly in my mind to find out the reason (though I know I can never explain it). Then I will experience the second state: trying to solve the problem and seeking help. If that fails, I will experience the sadness state: I keep comparing the past and the present, question the very reason for my existence and get inside my shell. The sadness can be accompanied by mourning as well. The sadness will gradually turn into anger. I blame the possible cause, blame the possible people who cause the problem, blame everything. Gradually, I come to accept the reality, though the hatred will still go with me, and when I see those possible people, the uneasy feeling of hatred still overcome me.