The word "believe" has a strong affiliation with the word "faith", which states, hoping on a particular thing even without seeing it, or seeing it happen at the point in time.
Growing up, I'm sure most of us at some point in our lives has been told, "I believe in you" or "believe in yourself", by either a friend, colleague, loved ones, etc.
It's quite important t, that in all these motivation and talks, it is very crucial and necessary for one to first believe in his/herself, because no matter the inspirational or motivational talk, the strength lies within an individual.
Whatever task you may want to carry out which may seem really difficult, remember you are stronger than you know, and as a human, we are only limited by our mind, and the fact is no matter how anyone believes in you, if you don't believe in yourself, then it's worthless.
Learn to believe and trust in yourself, because you've got the power to make things happen.