What is ur reaction when u meet something new at first time?
Refuse it? Accept it? Watch it? Try it?
Or some of them? Or all of them?

Do u believe u can make benifits from it? Will u spend some time and resources to try and explore it? When u take these actions, do u prepare to meet some obstacles and try ur best to conquer it?

Right, today when I tried to configure pptp connections for ubuntu 12, I can not make it for several times and even can not figure out what is the root cause.

The error is “EAP: peer reports authentication failure”, and there are some noisy output logs. How do u know what message is normal and what is abnormal? And what is the correct action to fix it? It is my first time to configure pptp. And I have no experience about it at all.

There are several times to make some unreasonable judgement.
However, when finally the config is done well, I do not see any difference between the config file that works and the config file that does not work.
That does not make sense.
So can I conclude that it is my illusion that does not cause my incorrect actions to make it work even for correct config files?