From my personal experience, it boils down to two things: Believe it’s possible, and never give up. Both are necessary to achieve success; both cannot work independently from each other. Both are mandatory for achievement because they complement and fuel each other.
You can try your hardest your whole life and never get anywhere. Do you know why? The answer is simple, Because you didn’t believe you could. The same applies in reverse; you can believe you can, but if you give up with the first, tenth, or even the 100th disappointment, you will ultimately fail.
Why? Because belief is needed; belief is the glue that holds your will and your intent together. Everything that exists, in reality, is vibration on all its planes, both subtle and physical. The act of belief, i.e., your will/intent is aligning your subtle worlds, representing your mental and emotional self with the physical via The Law of Attraction: like energy attracts like energy. It is only when our whole self is in harmony that we can succeed. If your vibrational alignment is off, you will be at cross-purposes with yourself, and it will be a downhill battle with results that are the opposite of your desires.
Determination (never giving up) is needed because we live in a physical world and the material world requires action before anything can manifest. If you stop taking action before you have achieved your goal, you will accomplish nothing.
To accomplish anything, one must first believe and then apply oneself until the desired result is obtained. For best results, always respect and honor others and practice gratitude for all that you have. In doing so, you cannot fail because the whole universe will be in accordance with your desired outcome.