You should try to plan ahead as much as possible. The proverb states "The plans of the diligent one surely make for advantage, but everyone who is hasty surely heads for want." Prov. 21:5
Make a list of things to do the next day and prioritize them by importance. Maintain a monthly calendar,as appointments and other assignments come up make sure you write them down.
When doing your major projects do them during a time where you are at your best.
Always keep track of time and allow yourself room between projects and appointments so you don't have to deal with the stress of always running late.
Delegate responsibility. Sometimes we are trying to do everything ourselves, when there are tasks that can be given to others to handle.
Take your larger tasks and slice them into smaller ones, as you go completing them you will notice the progress which will keep you motivated.
Plan for interruptions, allow time for things that can happen unexpectedly. When you do this it helps you avoid getting upset when things come up.
Reward yourself! If you've been working on something for over an hour and a half stop and take a brief brake. Stretch, take a drink, clear your mind then go at it again.
Following these steps can help overcome planning barriers, there is a principal in life which will never change:
"But let all things take place decently and by arrangement." 1 Cor. 14:40