First things first, anxiety is often paired with depression. It is absolutely normal to feel anxious or sad from time to time, but chronic, systemic depression and anxiety is something that should be addressed ASAP. Especially because this kind of depression and/or anxiety has a physical effect on the brain. Despite my desire to go into the details, I won't, that will be in my upcoming podcast if you are interested.
There are multiple causes for depression and anxiety; these could be situational (i.e. being isolated, house-bound, locked out of school and favorite activities for the last 2.5 years, or a brain injury and all the PTSD or PTRD associated), they could be purely chemical (anxiety is often triggered by thyroid conditions, and depression is commonly caused by imbalance of serotonin, dopamine, and/or norepinephrine, and it's another thing I have experienced, especially in the last few weeks), genetics or heredity, and are things that affect the self-esteem, such as: peer problems, obesity, long-term bullying, academic problems, the pandemic, etc. These feelings are frequently irrational, and often cannot be dealt with logic.
So, what can we do? If you know someone who is struggling with these things you can do, or if you are struggling, you can reach out to a friend and ask for these things. (That link is actually really important to go to). It is important to see a professional as well. I encourage both a psychiatrist and a psychologist. A psychiatrist will help with medications and a psychologist will help you talk through things, sort things out, and come to realizations and breakthroughs. If you are opposed to prescription medications, see a wholistic doctor, and more importantly, research supplements and what you may need. It is quite frustrating how long these chemicals take to rebalance themselves, and some of the brain damage may not recover until after the depression/anxiety goes away. As for the self-esteem, this one can be trickier at times. Seek people who love you to reassure you that you are worth it, that your flaws do NOT outweigh your wonderful qualities. One of those people is the Savior, and the Almighty Father, God. Please pray to Them frequently, asking with a sincere request to help you see yourself as they see you. If you know a priesthood holder of the church of Jesus Christ of Latter-Day Saints, ask for a priesthood blessing to be able to do so. They love you so much, they know of your infinite and eternal worth and the things you do are in no way associated with that worth. I testify of that truth, even when I don't feel it, I know it is there.