Talked to someone about my mental health and here is what I understood

Overthinking is not the fundamental reason/ root cause for a person to feel depressed or to be in depression. There are environmental and outer factors that lead to overthinking and later to biological reasons for a person to feel depressed.

Overthinking is not necessarily bad if it is directed towards positive thoughts. However, if overthinking is negative and is done to blame oneself then it can become a vicious never-ending cycle.
How can you handle overthinking? Make sure your mind is thinking positively. Of course, it is important to count the pros and cons of a decision/situation/condition but it is more important to know its purpose. What are the things that are precious to you? How much can you sacrifice for them? Are you taking care of your mental health during the process and why it is important to understand the real value of positive self-talk? These are some questions you need to think about and reflect upon.
Spirituality is another way to have positive self-talk or a positive mindset. Whether you meditate or practice yoga, forcing your mind to do positive things can help you induce self-improvement. The positive elements will help you focus more on the positive aspects of your life. But you must be patient as this process takes time. Maybe this is where our willpower comes in handy, to wait patiently even though the destination is difficult. You must understand that healing takes time, just like overcoming a vitamin deficiency.
Everyone goes through the hardship of life and those things cannot be compared. It is important to understand that overthinking is not a negative thing unless you are doing negative self-talk or forcing yourself into negativity. In such situations, you can find someone who does not judge you, who is there for you when you feel low without asking questions or you may choose to self-reflect in solitude. Family can help in such cases.
Otherwise, you can positively talk to yourself, shedding all the negative aspects of your life. There are many beautiful things around, you must remember. Even a bloom in winters can make us happy without much effort or thought. Life is easy without negative thoughts.
Exercising is another way to keep your mind and body synchronized positively. When we do not feel psychologically healthy, our body also reacts to the condition. We face sleep deprivation or over-sleep. We overeat or do not eat at all, isolating ourselves from people. Even a normal walk outside the house can sound like a very difficult task to complete. I had stopped feeling healthy, both, physically and mentally and it took me 6 years to snap out of it. I am still processing but I am better than I was one month or three years ago.
Feeding yourself positive thoughts and healthy food is crucial. These are some external factors that can help you constructively manage your stress and anxiety. You will feel healthy again, both psychologically and spiritually if you are having good food, good thought.
One more thing, many of us feel (including myself) that venting it out online will help us heal. I did that, unfortunately. It is not true, it never helps. Everyone has their lot and they are busy in their lives. No one is interested in your mental health or self-centered thoughts. Maybe they are facing an even worse crisis. It is a harsh truth. Looking for a support system online is a foolish thing to do.
To sum up, it is all about your internal well-being. Even outer appearance is affected when we are hurt inside. Do not be hard on yourself even if you criticize your existence, do it positively. Times are hard but they will eventually get better. Just do not go with the flow if it is making you sick. It would be better to act for yourself without waiting for anyone. But if someone is willing to help you, appreciate their efforts and acknowledge them.
I have tried many times to reach out to people but I am not doing that anymore. I have understood one thing life goes on, it depends on you how you want to take it.

This is all available on YouTube or self-help books. It is just a reminder to me, to people like me, who can do whatever they want if they stay strong.