[jaydub]

It's a lack of experience, self confidence, and self worth. That all leads to the focus on one particular girl whom the OP barely knows. As others have mentioned, OP probably lacks significant dating experience, certainly does not truly believe he is a desirable man, and this shows through his behaviors.

He has constructed this perfect image of a girl he barely knows because she has paid him some attention and has desirable qualities. This attention is not something the OP is used to receiving and he craves more. Due to his lack of inner strength and confidence, he feels that this is a special situation that he must pursue to the end.

What makes it worse is that this girl likely pays such attention just for the multiplied attention she receives in return. OP is not the first to pine after her to no avail, hell he may not be the only one currently doing so. Whether she does this consciously or subconsciously is up for debate put the result is the same.

All this advice on how to get this girl is irrelevant and misses the central point of why try so hard. Unfortunately I suspect that convincing the OP and the bulk of the posters of this will not succeed. Much like convincing someone not to play KQo for a big raise will not succeed.