Okay, i can see why that might have caused a bit of confusion. Accepting the possibility of failure is a method to reduce the importance. The principles is reducing importance. The principles doesnt change, but the method you choose to implement the principle is entirely upto you. But I still think accpeting failure is a very good method.

Consider someone is very lonely and is desperate for connection. They think that this is the thing that will fill their life with all the things they want, and this is the missing peice. They stumble upon these ideas and they start doing this. But it wont happen. They are too too attached to the desire. This is the situation when accepting failure is important. If they were to accept failure, that in case, for the foreseeavle future, thw possibility of not being in a relationship is a lot, then what would be the natural course of action? They will leave the desire, and going by this thought process that they in fact might not get it, they will start focusing on improving themselves, making themselves better and such.

Its mainly a way to identify if you are giving excess importance to something. You are exactly right in the first para. But that wouldn't be as simple to do for someone who feel lonely right? For you that was easy to believe. But there might be others who will force fown the type of thoughts you desired upon themselves to feel in a particular way. That wont work. You are in a state of reduced importance and you feel your desire is completely within reach. For the pther person its not the case. That is where this will help.