In our world of web tech, or technology in general, tools and techniques tend to be transitory and ever changing. Even after fifteen years of doing web design, I still have trouble believing that I can really build a future on technical expertise. I know that design and problem solving skills will never lose their relevance, but with html and css, I sometimes struggle starting to learn some things, because of fear that they might go away soon. But I love learning, so I do it anyway, without regard to the usefulness of it.
Just after learning the basics of Grunt last autumn, my friend jokingly said to me: "I six months, we'll switch to Gulp!" My heart skipped a beat. I had just learned to manage a build system for the first time on my own and it was already on its way to being obsolete. Of course sometimes you should stick with what you know and not switch immediately to the new shiny thing. It took a long while for me to get going with SCSS too, because I did just fine with regular CSS. After dabbling with SCSS for a couple years I had made a few hobby projects where it really saved time and effort. When I felt comfortable with it, I started using it for client work too.
So don't be afraid to learn something new, but don't rush using that new thing for production work until it feels familiar and solid. Some things will stick and we will build on them for a long time.