Everybody has a cup of sand in their life. This cup of sand represents their mental well being. When the cup of sand if full, life is good. You are happy with friends, family and the responsibilities that you have. Each day, when people need something from you or have demands on your time or attention they use a shovel and take a little sand. Some people have bigger shovels and take more sand than others. As the day goes on your cup gets emptier and emptier. When your cup becomes empty you get tired, angry, irritable and just want everyone to go away. The only way to refill your cup is to do something that you enjoy. That can be something outdoors, vacation, reading, quiet time... whatever it is, it is necessary to fill your cup.
My explanation for depression is that depression pokes a hole in the bottom of that cup. Some holes are larger than others. What this means is that no matter how much you do things that you enjoy, it isn't filling your cup of sand and you see no reward in doing them. So you stop doing the things you enjoy. The emptier your cup gets the more protective you get of the sand you have left. You push people away that have the largest shovels including those you love. Your mind comes up with problems and issues that don't exist as a reason to push them away. Eventually when that doesn't help you start pushing away the smaller shovels as well until you are all alone.
It becomes harder and harder to fill your cup back up so you will literally turn to anything that makes you happy. Affairs, drugs, alcohol, self harm (cutting). What ever it takes to make you feel better and fill your cup you will do. You are not thinking of other peoples feeling or lives at all. You just need more sand. Whatever gives you that sand becomes addicting. I was (and still am) addicted to that feeling I get when a woman flirts with me. I have learned to recognize it and control my actions but it is HARD. If you can't find anything that makes you happy suicidal thoughts begin to creep in. Small at first but the emptier that cup gets, the louder those thoughts become.
Things like therapy and medication can make the hole in the bottom of the cup smaller and in some cases close up completely but it takes a lot of work. I have been dealing with this for almost 5 years or more now and I am just coming to the realization of how to deal with it and recognize it.
A person once told me "It is literally impossible to think of others when you are on fire." This is so true! Depression is a lot like being on fire. You don't mean to hurt people you love but you have to fill that cup back up even if it means taking risks and hurting others. You're seen as selfish and mean but your not. You just want to put the fire out. You want a full cup like normal people.
Using this analogy has helped me explain depression to others so that they can better understand me. It has helped me understand myself better as well. It gives reason to the weird things I do and why I push others away. But it also helps me remember that the cup will fill back up. I just need to find the good ways to do that.