Things don’t go as planned. Instead of fighting it, make that part of the plan. Things will take longer than expected. Interruptions happen. You can’t control other people’s schedules or work. So many unexpected things can happen. Factors beyond your control change.
When things don’t go as planned, you can get new information. That new information can be very useful and it can lead to new things better than the original plan. You might see new opportunities. You might be forced to think differently. You might meet people you might not have otherwise. New steps along the path.
Of course, this is not to say to not have a plan to start. (If you simply take things as they come, you’ll get nothing done.)
It is more about recognizing that trying to stick to the plan at all costs is the wrong way. Too many unexpected things can happen. If you are too rigid in trying to stick to your plans, you set yourself up for disappointment and frustration.
Make it part of the plan to not have a plan. Start with a vague plan, play a little. Move one step at a time, learning from the previous and building from there. Plan to learn from and build upon the unplanned things that will inevitably happen.