I would start off by just saying it’s important to believe in yourself because…and I would say three reasons.
Then for the next three paragraphs I would explain each reason.
Then the conclusion
Some reasons you could say are:
1. If you don’t believe in yourself you won’t be brave enough to make decisions confidently
2. If you believe in yourself, you can succeed
3. If you don’t believe in yourself then others won’t either
4. You limit yourself in so many ways by not believing in yourself
5. You miss opportunities