It is not easy to be kind to ourselves although there are a tremendous amount of reasons why we should be. These reasons include health, completion of goals, and social harmony.
To be kind to yourself means that you are willing to take a broader perspective of your judgement or analysis of yourself. You are willing to go beyond the involuntary emotions and impulses that arise, and instead seek solace in some kind of wisdom. This wisdom must be earned through repeated failure and learning from it, other wise it will remain intellectual information rather than knowledge.
When you do something that is disappointing to you, it is helpful to recognize that there are multiple versions of the self that is residing inside you. There is one part of you that is reactive and simple, there is another part that is analytical and complex, and finally there is the part that is transcendent and somehow connected to a greater reality. They are all valid and fulfill different functions, and accordingly have different priorities.
The complex part of you may make plans. For example that you will wake up early tomorrow. The simple part of you will have nothing to say about that in the moment because at the time you are making the plan it is looking at some short term requirement such as that you are hungry or sleepy or bored. Then the next morning you try to wake up, and the simple part of you just can not fathom getting out of bed, and this complex part of you seems to be some far off dream and can barely be heard. So the simple side wins over, and then suddenly it is 10am and you jump out of bed in a rage. You are scolding your self, and really you are scolding your simple self.
But in this moment, I urge you to recognize the reality of the situation which is that your simple self was really just too overwhelming for your analytical self. You can not slice off the simple self from the personality. You can not wrap it up in a bag and drop it off in the trash. It is a part of you. There must be another way. Perhaps that means sleeping earlier, or not eating food too late, or staring at a bright electronic screen just before you try to go to bed.
So we see that being kind to yourself is not just something you can force on yourself in the moment. It requires planning ahead to make sure that the needs of your "whole" being with it's many different parts are being met. And when they are not met, do not be angry that you are not a super human. Recognize that not everything is in your control and situations bigger than you prevented you from executing your plan to get to bed on time, so that you could wake up earlier. Try harder next time. It is in the trying that you will eventually create the reality you intend to. Not from force of will, but from force of habit.
True we may wish that humans are not the way they are, but it is what it is. The mind is made up of a family of processing centers, not just one that is glued all together. Observe the complex self and the simple self, how they interplay and one is dominant at different times. Learn from the experience and I wish you the best of luck in being kind to yourself.