There are times when we were told you can succeed, but our self talk/ disbelief stopped us achieving the success that others believe we can gain.
Self talk has very strong effect on outcomes of personal events, often causing us to create ways to manifest the negative instead of the positive to maintain harmony within.
Our self belief prevents us at times setting personal goals that we are capable of achieving with a little challenge, rather setting ones we can gain with ease.
A couple of quotes that highlight this are
The greatest danger for most of us is not that we aim too high and miss it, but we aim to low and reach it. Michelangelo
Start by doing what is necessary; then do what is possible and suddenly you are doing the impossible. St Francis of Assisi