1. Assume something or someone will frustrate you in some way. They will stand in your way, block you or slow you down.
2. Assume that you are likely to respond well to some of these frustrations but you will also not do as well as you would like with some other frustrations.
3. Assume that some good things will occur or some near misses of bad events will occur.
Then prepare yourself in advance for the first two assumptions above. You do not need to prepare for bad events that almost occur later today but fail to materialize and you do not have to prepare for the good events that will occur. However, it is good to recognize that good and bad will occur just for a balanced view.
As for how to prepare yourself for the first two assumptions above fall back on REBT philosophy. Remind yourself that people and events do not have to be as we would ideally like them to be. It would be lovely if they were always as we wish they would be, but if things were always this way you would be living on planet Utopia, not planet Earth. So, join the rest of us down here on planet earth and prepare for the inevitable hassles and inconveniences of the day before you by holding a flexible and non-extreme attitude towards the frustrations that will block you. Those things should occur once they do because the universe permits this to occur. Rather than whine and complain and turn a hassle into a holy horror, try accepting that these things happen. If you do this the healthy negative emotions you will feel will be annoyance, displeasure, disappointment, sadness, and concern and these feelings will motivate you to change what you can change or permit you to emotionally move on sooner rather than later if what is occurring cannot be changed. These healthy negative emotions will be feedback that something you do not like is occurring. Nonetheless, these healthy negative feelings will not consume you, lead to self-defeating behavior, interfere with creative problem-solving, or undermine sustained persistence at changing what can be changed. These healthy negative feelings will allow you to have some happiness despite the presence of the bad event.
As for preparing for the missteps you may very well make in responding to the challenges of the day, remind yourself that no matter how intelligent, well educated, and diligent you tend to be, you will occasionally mess up. It is our nature to sometimes trip ourselves up. Humans do it and that is bad but not awful. We are fallible beings. Strive to unconditionally accept yourself when you either misbehave or when you do not perform perfectly well later today. Then evaluate the actions you took or are now taking and if they are ineffective, bad, or less than ideal stop and act differently going forward. By unconditionally accepting yourself you will be less defensive and better able to more quickly adjust your behavior.
In short, remember to practice REBT’s unconditional self-acceptance, unconditional other-acceptance, and unconditional life-acceptance and do not yield to the seductive emotion of anger. It will defeat you as you try to change what you can change and accept and live as happily as possible with that which you cannot change. Watch and see how well philosophy works!