I find making plans to be the easy part. The hard part is sticking with it, day after day, week after week.
Yes, sometimes plans need a little adjustment and fine-tuning along the way. But I find the biggest reason that plans don't work out, is that we don't stick with them long enough.
See what happens when you make a plan, fine-tune it, and then stick with it. The result of following a plan is the sweet reward of progress. :)