SMART is an acronym here.
Each letter stands for a favourable characteristic of good goals.

Specific

Goals should be specific. Try to be as specific as possible about what you want to change.

Measurable

Goals should be measurable. So, keep a record of which measurable
values (e.g. working hours, number of pages written, chapters completed) you will use to notice a change.

Attractive

Goals should be attractive and achievable. So, it should be a change that you really want to and can achieve.

Realistic

Goals should be realistic. So, it should be a change that you can bring about yourself and that does not depend on luck or coincidence. Nor should your goals be too distant or too ambitious.

Time-Bound

Goals should be time-bound, i.e., limited in time. Keep a precise record of when you want to achieve your goal. Make sure that the goal is not too far away.