Here are some words I have saved from reddit, no source unfortunately:
Depression isn't an emotion. Depression has no cause. Too often is depression conflated with sadness or anxiety.
Depression, when it is present, is more like the force of gravity. It is there, pulling down on you under all circumstances. Though I'm depressed I am often very happy- but still there is the unfeeling wet blanket of muddled confusion and writhing frustration seething under it all. Waiting.
A creeping numbness that insidiously degrades and diminishes every aspect of conscious life. A storm of screaming and hatred in dreams. A dull apathy in waking. A sinking stomach in the face of joy and a faithless lassitude in the face of hope. Depression isn't an emotion. Depression is a contradiction to every worthy aspect of life.
It starts with something simple; maybe a rejection, or a social faux pas, or a harsh word from someone. Whatever it is, it plants a seed of self doubt in your mind that won't go away. This leads to a consistent feeling of self hatred, the feeling that you are somehow unfit or that everyone would be better off if you weren't around to embarrass or annoy them; you begin to isolate yourself because of this.
The longer this isolation goes on, the more persistent the feelings of inadequacy become. It becomes harder and harder to shake the perception of yourself as an essentially worthless person. Outwardly you maintain a persona, smiling, laughing, socialising, but on the inside you feel like you are slowly being ripped apart. If you're like me, you feel very strongly that you cannot share these feelings with anyone; perhaps you are afraid that they will confirm your worst fears about yourself, or they will belittle your problems. Perhaps like me, you're afraid of being stigmatised as a basket case, or having your masculinity questioned because you're a man who talks about his feelings. In any case, instead of seeking help you bottle your feelings up. Slowly and painfully, you begin to disintegrate on the inside. You push friends and family away, believing yourself to be unworthy of them or not wanting to worry them. You lose interest in things that you once loved, able only to procrastinate and wile away your time abusing substances. You neglect your physical health, hygiene and work commitments; concepts like hours, days and weeks become meaningless as your life blurs into a meaningless sludge alternating between when it is light and when it is dark outside. Your brain seems to be fogged constantly, similar to the aftermath of a heavy night out, and thanks to your inability to have proper sleep you are constantly exhausted.
Eventually you hit rock bottom; you sleep and eat far too little or far too much, and things such as dressing yourself or brushing your teeth become not only monumental challenges but seemingly pointless. The only thing that stops you from ending it is your fear of the act, your guilt over the consequences and your complete lack of drive or energy. You have forgotten what it feels like to experience love, joy, excitement; all that persists is the exhaustion, the anxiety, the embarrassment.
At this point you no longer experience what it means to be human; you are a husk, a body robotically carrying out meaningless tasks. That is what depression feels like.