In the wise words of Richelle E. Goodrich (American Author)
"You may be the only person left who believes in you, but it's enough. It takes just one star to pierce a universe of darkness. Never give up."
In my opinion, If you don't believe in yourself then everyone else in the entire universe will always take you for granted and no one will ever think twice about you.
Your belief in your abilities defines you. If you start second-guessing your abilities in front of the others then you already lost the battle. The moment people see that you have self-doubt, it's over because after that all they will do is take you for granted.
The best way to believe in yourself and acquire confidence in a very short time is by following these steps
1. Remove all the Clutter from your life.
2. Focus only on one goal.
3. Make your life as simple as possible.
4. You can't master everything but you can always master something.
5. Don't waste your time multitasking. It's the enemy of Confidence.
For example, Let's say you want to learn International Relations but at the same time you are also interested in Democracy, Politics and Geopolitics.
Let's say you have two methods in front of you
1. Method A - Multitasking, in this method you start reading everything from International Relations to Geopolitics.
and let's say every single day you have 4 hours of free time and you decide to divide it into 4 parts for each subject.
Result - By the end, you will have 365 hours of International Relations wisdom.
2. Method B - You Remove everything else and just focus on International Relations for the entire year.
Result - By the end, you will have 1546 hours of International Relations wisdom.
And within a year you will be a master of International Relations and your belief in yourself and your Confidence would be as strong as the English of William Shakespeare.