The hardest part about self-improvement is getting rid of biases which come from society, school and the environment we grew up in.
Since childhood we receive immediate feedback for our efforts in the form of reward or punishment: grades evaluate how someone has accomplished a task and do not consider context -where someone comes from- and whether someone is exploiting the system or has truly interiorized the lesson. This leads people to develop a result oriented mindset and to lose track of true personal growth; more specifically we focus on "whatever works" (linear thinking) and not on the process (circular thinking) itself.
Circular thinking starts from our prejudices -what we already know and what works as a mental paradigm to judge new inputs- and challenges them as soon as we receive new verified informations; this leads to a paradigm shift and to the shaping of a new, broader, horizon of thought. In order to self-improve we need to constantly reshape it and to look back at what we thought, said and did from a higher level of context and without being judgemental.
Self-improvement is hard because it requires a lot of work to build positive habits in absence of immediate feedback; in a certain sense it's a sort of leap of faith because we are committing our time and our energies to something which might not even work at all and, even if we've read inspiring stories or heard them from friends, the confirmation bias is going to trigger a skeptical response due to the lack of immediate results.
Self-improvement requires a whole new conception of learning and a different mental framework. We approach learning as a process and we accept mistakes as parts of our journey to our best-possible-self, without feeling regrets. We develop a sense of gratitude and feel proud for our own accomplishments; it's extremely important to be self-critical and self-aware, but this shouldn't lead to self-bashing.
This approach works both in personal and in professional life and broadens our horizon of thought. It's being able to recognize the harmonies in the songs we hear; it's being able to taste every different flavour in a glass of wine; it's being aware of the ideas behind major and minor events. You can have great results in different areas by taking shortcuts, but the only way to improve as a human is to embrace complexity and contemplate the different colours of the spectrum.