I went thru at least 30yrs of chronic serious depression starting in 10th grade. Some causes are known others not. For me I think it came from a very weak self image with lack of assertiveness. I'm very good looking and popular with people but many authority figures-employers, teachers hated me for sure.

I had great parents and friends. Dad took me hunting and how to work on cars, he and his four bros were in WWII and mom was well what mom's usually are. Neither parent ever criticizing or belittling me so where this self image came from I don't know.
Other times I think depression has no known cause outside chemical imbalance. For me there was no hope period. was afraid to kill myself thinking I could get stuck in some astral hell.
Talking to from friends and family was totally useless. It's beyond reason and common sense. But here I am. My mood is most always great and upbeat. Just hang in there and you'll outgrow it. Read inspirational quotes-they have very real value. See a dr. for meds. They did wonders for me. Read up on REBT therapy very popular. Look at what you're telling yourself. It's for sure exaggerated and irrational. All little things help. Exercise even just walking is a premier cure for depression. Don't look for perfection in anything. Send out love to self and others by just saying things like "I send love into my personality" or 'i send love to whomever is irritating you' You don't need to act at all-just the thoughts will program you. Don't forget meditation-Like this- get comfortable, count down from 10, feel your breathing get shallow and slow. Ignore thoughts and images. You are looking for the alpha state which is the quiet mind before sleep sets in. If you're thinking you're not in alpha. It's where your intuition can communicate to you. That's it. The Beta mind or fast thinking mind is only full of thoughts and images from the past that tell you they are extremely important and need to be addressed.