Drawing up a plan is work too, and the quality of doing it comes with experience. You should not expect to perfectly lay out all the steps for each goal on the first try, or to plan them skillfully on your calendar. Especially if you consider that your goals may involve competition, depend on other people, or resist precise description (for example, renovation or achieving sports results). In such cases it is unlikely that your first plan will be ideal. Think of it as painting a picture — and right now it is only a sketch. The next approach to the canvas will be better: you will already have more experience and will be able to draw something more concrete.
Nevertheless, there is one good methodology I can recommend. I borrowed it from Daniel Kahneman, who briefly described it in the book Thinking, Fast and Slow and called it the "outside view." The principle of this methodology is extremely simple: if you are planning something in which you are not an expert, ask about all the nuances someone who understands it or has at least been through something similar.
In the book Kahneman describes a situation when he and colleagues were writing a psychology textbook intended for use in government institutions. They allotted an extremely small and unrealistic timeframe for writing the material — one or two years. In the end the process dragged on for more than five years, and to be precise, writing and publication took about eight years. Ironically, Kahneman asked the opinion of those who already had similar experience, and they immediately predicted exactly such a long timeline, cutting off all his initial optimism at the root.
Similarly, when planning an important task — say, renovating an apartment — be sure to ask friends who have already been through it: what pitfalls they encountered, how much time and money they spent. If you are quitting smoking, find those who succeeded and learn from their experience. All of this will help you be more accurate in your forecasts. After all, the outside view is often more accurate than the inside view.
