せっかく and だから are used when a rare or unexpected situation has come up, and it would be a waste not to make use of it.
The situation appears between せっかく and だから. However, the situation is often left out when clear from the context.
- Kamiya, Takeo. “Adverbs Expressing Circumstances.” The Handbook of Japanese Adjectives and Adverbs, Kodansha, 2002, p. 191
- How to use せっかく ( = sekkaku) (maggiesensei.com)