When depressed, why do the smallest of things sometimes just send you into this downward spiral that won't stop?

Because the smallest things never feel like the smallest things. When you suffer from depression, things like getting of bed, eating three meals a day, and remembering to take your pills are major victories, so when you suddenly burn your toast or give the wrong answer in class, it feels like a huge failure. You make all this progress and then you mess up on something you want to perceive as "small" but that small thing really bothers you.

Sometimes when we are strong for too long our "cup" gets a little too full. So that one little drop over flows our cup and we tend to breakdown. When we already down, that one little drop can affect us a bit worse.

It feels like absolutely nothing is going your way, because sometimes you expect big things to have a variety of outcomes, but you seek comfort in routine things that rarely go wrong. When these routine things go wrong, it can feel like every possible thing is going negatively.

Sometimes, little to nothing can feel like a lot when you don't know exactly what we're feeling. The littlest things can trigger something so large and it's hard to explain why. It's just when we feel sad or numb, our body wants us to feel more so the triggers can make us start to feel something even if it's just more sadness.

Depression causes an imbalance in your serotonin levels, serotonin acts as a mood stabilizer. Therefore if even the slightest thing triggers your symptoms of depression or sadness it can seem more extreme than it actually is. This however is normal when suffering from depression and nothing to be ashamed off.

Depression is often when you feel like life is getting to you so much that you just can't help but feel like everything is going to make your life worse. You made a spelling error, you must be stupid. You accidentally set the oven 10 degrees too low, you must be an idiot. All the little things in life make you feel bad because you already feel bad and have the mentality that everything that seems normal to most, is the worst thing ever when in reality, it's not. Life is full of challenges but always remember that you're in control of you. Don't let depression take you down. Shrug it off and move on. Force yourself to realise how insignificant it really is by rationalising it anyway you want. Take control of your depression, don't let your depression take control of you.

Because depression makes me incredibly sensitive and self-critic, and then I tend to perceive information in the most negative way possible - and believe in it.

Depression likes to suck everything it can out of you, if it can find one little thing to overthink, it will. Then another... then another... Spirals suck. Just remember that when you tell yourself you're worthless, or that you don't matter, or you're not good enough, it's not true. Keep moving forward, you're a good person and you matter.

When you're depressed, you feel things at higher intensities, you can detect a slight change in the weather like a friend died. Small things affect you extra. You're thinking a lot more in general and a single event might trigger you to just start listing out everything wrong, whether it has an immediate consequence or not. Try writing out every single thing that's worrying you and then categorize them into 3: work on now, not important right now, and maybe worry later. It might help you think more clearly.

When you feel depressed, mostly everything is seen negatively and can break you down. I'm sorry about the depression you're feeling.