First you, or someone else who knows you well, may have to decide whether you might be clinically depressed. If you are clinically depressed, you will need to get medical assistance, either through counseling or medications or a combination of both. It doesn’t help, like @gailcalled to have weird, outdated and silly ideas about depression and how it is treated. Depression, like diabetes, is a medical condition that can’t be figured out on your own. But if you are clinically depressed and you choose not to get help, then there’s nothing any of us can do and you’re likely to get worse over time.
Also there are different types of depression, which you can read about on this link from the Mayo Clinic
You can also read about the different types of Treatments for Depression
That being said, if you are just experiencing a slump, which most of us do from time to time, then you probably need to change the way you look at things and change the actual things you do.
Sometimes seeing things from a different perspective can change the way you actually think about things. Volunteering is a good way to do that. If you are sitting around your house, laying on the couch like a potato, eating cheetos and watching TV, you can’t really imagine what it might be like for other people, like disabled people, or the elderly or poor people. If you volunteer for a soup kitchen, or go to a retirement home and read to people or play music for them, if you’re so inclined, or volunteer to drive people to and from doctor appointments, you can get a very different idea of how awful you think your own life is. You might become grateful for what you have, instead of pissed and moany about what you don’t have. If you’re a good volunteer, you might make lots of friends and actually make other people happy. That, in turn, will hopefully make you happier.
You might also want to try new or different activities from the ones that you currently participate in. Sometimes mixing it up can really change your attitude. If you like sports, try a different sport from the one that you usually play. If you usually do team sports, maybe try something more solitary like surf paddling or roller blading. If you usually do rough and tumble ball sports, try something more refined like yoga or ice skating.
Is there anything that you are interested in, or have contemplated, but haven’t yet tried? Now’s the time to try some of those activities. Some of my personal favorites are cooking, photography, hiking, camping, painting & drawing, interior design, traveling and writing.
Are your friends boring? If so, try to get them to try out some of these new activities with you. If they refuse, then go along to some activities that have clubs or organizations or groups of people that participate in the activities. You might meet a bunch of more interesting, less boring people that share common interests with you.
If you are stuck in a food rut, especially a junk food rut, go to the store or a local farmers market and get yourself some delicious, healthy, fresh produce and make some salads, or sandwich wraps, or stir-fry or homemade soup. Try some veggies that you’ve never had before, or try using veggies that you know in different ways. If you always eat something raw, try roasting it. If you only use lettuce in salads, try using lettuce leaves as a wrapper for something like This
Do you spend a lot of time sitting or laying around? If so, decide right here and now that you’re going to get up and do something. Exercise would be a good start, and you don’t have to kill yourself to get a little bit of exercise. Go for a walk or a bike ride or a swim.
I guess the short answer is, figure out what the problem is first, then make changes, big and small.