@YOUKNOWWW420 depends on which area it is about. But tbh, most of self esteem is a fake it till you make it thing, so don't stress if you don't get it right away, keep faking it, one day it will come.
If it is about your looks. Try to write down things you like about yourself. Can be as small as your eye colour. And if you find that there is not much of that. Then go with things your body does for you.
If it is about your personality, try exploring who you are with a little self love. Write down what you like. Your hobbies. All kinds of different things, get to know yourself. And you will soon find out you are actually a very interesting person.
If it is about skills, keep track of compliments you receive at work/school. Take an approach of "I'm learning and working on being better". Take opportunities to grow. Work on your skills. Take opportunities to learn from your colleagues and take courses. Also, if it helps you. You went through a hiring process. They hired you because they saw your potential. Also, workplaces won't assign you the hard And most important tasks right away, you start from the easy basic and work up. So if they assigned you something, it is because they believe in you and you should too. If you have your doubts or need help, you can always schedule a consultation with someone who you look up to. You will get a lot of interesting insights from them, they will be happy you look up to them. And if you are at school and your self worth is tied to grades. I can assure you. Noone has ever asked me what did I get on that end year math report. Noone. Ever. It seems like the world now, but trust me, noone will care. I can totally say it with confidence despite being just 23. Noone cares. And the older you are the less important it is. Rather, choose an area of studies that interest you and you want to work with something related in the future, and pour yourself in that part. So if you are interested in math related subjects, focus hard on physics, maths, chem etc. and if you have bad English grades. Oh well. Just make it enough to pass and have some basic knowledge. So making peace with not being good in something as much as it seems contraproductive, will also boost your confidence a lot.
If your self worth is tied to how well you are able to communicate with people, then it is time for some comfort zone pushing. Pick a specific area as a tiny challenge you will work on. Like calling a friend or inviting them for a coffee to get some Human interaction experience. If you do good with friends and family but struggle with strangers. Call the next time where you would write an email. Order in person at McDonald's instead of using the self checkout. Ask an employee in the store if you can't find something. You will absolutely not like it. But it will get easier with time.
Now some universal stuff:
Address mental health problems and possible traumas, search for where this self esteem issue started and where is it coming from. You can do that through journaling or with help from a mental health professional.
Keep addressing the challenges you face in the present. I personally love the journaling format of structure like this.
1. What is bothering me -absolute brain dump in points. This helps you organise your journaling better since your brain will be later able to focus on one at a time instead of jumping up and down pointing to new issues
2. Writing out each individual point and elaborating on it, letting my brain talk itself out. Then, once your brain said all it wanted about the point, ask yourself what will I do about it now? Validate your feelings and suggest possible solutions and tiny steps you can take to get there. When done, address the next point
Gratitude/compliment journal, where you can write things you are grateful for or nice things people told you
Use thank you language instead of sorry. Instead of sorry I'm late say thank you for waiting for me! If you want to say sorry I bothered you with this, say thank you for helping me out/explaining this to me. Swapping constant apologies for thank you can make such a big difference.
Practice self love in any shape or form you need. Be your own best friend. And you will see how much more at peace you will be