why is it so difficult to rank using white hat?

The job of the White Hats is to rank lower so that Black Hats can give search engine reps a reason to keep their jobs.

That is, WE are the reason Matt Cutts has a job. Imagine if everyone did what he said : "drink tea, watch puddles gather rain, NEVER spam ok, NEVER". There'd be no spam, he wouldn't have a job, we'd all be sad.

Black Hats are the reason Matt Cutts doesn't need payday loans. That's all there is to it.

Unless you tell us what you've done for "white hat" SEO, there's no way anyone can seriously advise you.

White hat method takes time to deliver the result but results are durable black hat method takes less time but results are not durable. So always adopt the white hat strategy to do work because always keep in mind this phrase "slow and steady win the race".

I agree. It really takes great effort to succeed doing the white hat techniques, but they are all worth it. Just review your tactics and be open to make some changes if needed.