>>2 Is right. As for any immediate action you can take, perhaps writing your sentiments/voicing your feelings and thoughts of the moment to yourself would help. I, personally, believe that doing so would at least help you clear your mind and slowly understand what might or might not be the cause of your sadness.
Of course, if you are proficient in any for of communication, be it art, music or etc, you might want to consider those too. Browse for a video that would resonate with you? Ultimately, if possible, consider sharing bits of your trouble to someone you trust.
I, personally, trust that you will overcome this (you have the strength to refuse to effect others even in this mood). Good day. :)