The best thing you can do when a plan doesn't work, is to start a new plan.
We have many plans. Some work, some work slowly, some don't work at all.
I have found it to be a good thing to have a look at my yearly plan every three months or so. What is working? What is not? And then I tweak as necessary.
I don't plan for the whole year in great detail, as life happens, and plans need to be reviewed. We change, situations change, we find new desires to reach for, and realise we no longer have passion for something we have started. We are not the same person a year from now.
Don't force yourself to follow a plan you once made if it doesn't feel right anymore. Plan the major lines, and fill in the details little by little as you go along. A little more in detail for a month ahead, and then in greater detail for the next week.
You can never plan everything beforehand so that nothing changes. If you try, you'll just end up frustrated.