The most commonly found attempt to alter yourself requires willpower: you decide to do something. Intentions can succeed. If they fail, then it is rarely because you did not desire it sufficiently, instead, from our point of view, it is because there are unconscious forces which are directed against this intention.
In such a case it does not really make sense to strengthen your willpower. It will, almost certainly, lead to new failures and with it, to a reduction in self-esteem (“I cannot manage this!”). Instead, it is important to engage with the hitherto unrecognised and perceived internal counterforces. If someone doesn’t persevere, they have reasons for this, which have not been perceived, or to which they have not attached significance. To alter this, you almost always require a competent opposite, i.e. coaching.