I'm not talking about quitting your job and starting a new career--that is, unless you're prepared to do so. Doing something new might be as simple as taking a different route to or from work. Or it might be learning a new skill; volunteering; mentoring a child; learning another language; eating something you've never eaten; eating a healthy meal; exercising--even if it's just taking a walk; planning a trip to a state or country you're curious about; taking a free online course (see sources under Miscellaneous); inviting someone to dinner; paying for a stranger's coffee, meal, gas, groceries, etc. It needn't be anything big. Something small can make a large impact. Who knows, it just might lead to you realizing a dream.
I happen to think that once you try something new, you have everything to gain. Even if things don't work out as you hoped or expected, at least you tried. You took a step forward. And maybe that will give you the strength, courage, confidence, satisfaction, perspective, and enthusiasm to take another step, to try again, or to try something (else) new.
Are you willing to try something new?