せっかく
Usage
せっかく is used in the following situations:
when the speaker does something with a lot of effort or at great pain and therefore wants to make use of it, in spite of the effort or pain
when given an opportunity is a rare one and therefore wants to make use of it or in spite of this opportunity, cannot make use of it With effort; at great pain; take the trouble to do
Examples
せっかく日本語を三年も勉強したのだから、ぜーひ一度、日本に行ってみたいです。
With great effort I have been studying Japanese for three years, that is why I surely want to go to Japan once.
せっかくケーキを焼いたのに、誰でも食べてくれなかったから、がっかりした。
Despite baking a cake with much effort, I was disappointed because no one ate it.