>>1 they're just dark thoughts that, like you said, everyone gets. The way everyone deals with them differs. There are many ways and it really depends on circumstance and mental strength.
When my dark thoughts get too much to handle and my conscience starts yelling, my head just gets so loud... I listen to loud music, usually Alexisonfire or My Chemical Romance.
Other dark thoughts I put on paper in my drawing and my writing, and sometimes I practice singing a song that speaks my feelings.
Another way is to find people that make you laugh and make you happy or even treat yourself to your favourite snack. Just find happiness to overpower those dark thoughts.
I hope this helps answer your question ^^