Thinking fluidly
As an in-house designer in tech, the company brand becomes your favorite big sister (or little sister when you find her hard to wrangle). Working in-house, versus an agency, allows the brand to sit in your hands. If you have a seat at the visual table, yet letting the brand sit with the grandeur and finality of the Constitution of the United States, propped up in its glass box, then you're not doing it any favors.
I believe a brand is a living, breathing thing. And if you're in the driver's seat (or in the car at all), it's your responsibility to make sure it doesn't stall out. A brand should always be evolving. When a rebrand occurs and a new style guide and brand book is developed, that's the starting line, not the final word. At my last company, it was my responsibility to tweak the brand book quarterly and update it based on the ways the visual identity and messaging had evolved in marketing materials throughout the quarter.
No matter how robust a brand's library may be, create enough ads, social posts, emails, ebooks, webinar graphics and sales materials with it, and you'll see you've used every expression of a shape and every color combination at your disposal.
If you work somewhere that allows you even an iota of creative liberty, it's your responsibility to lead with curiosity, and see how you can push and continually improve upon the visual identity. Try to break it. See how far outside the lines you can color with it a visual identity. You might then be asked dial it back, but sometimes you have to go too far to reveal the possibilities to yourself and your coworkers.
Getting reinvigorated
I've taken the outside-the-box approach to a ridiculous, frankly un-workable level. What if, as a break from your day-to-day, you were to make the brand look, well, not like the brand? I've tried this by playing with my company's brand in a different color palette, and shape, pattern, and photo library — something I'd never present as a real idea.
I've seen my design friends, and myself, feeling stifled by exclusively designing within the brand of the companies we work for. I found this exercise reinvigorating. It's finding a way to be super playful while still being in the realm of my real-life goals and responsibilities.
I never expect my explorations to come to life within my company's brand, but this exercise has a) allowed me to take inspiration I've found from outside sources and see how they could radically be applied to my current brand, and b) it's gotten the gears turning with a lens I hadn't previous positioned toward the brand.
Being observant
As a designer you must continually be on the search for what inspires you. Notice when a brand's social media style isn't correctly aligned to their website design. Notice when the look and feel of a brand doesn't quite match their audience. Continue forming and stating your strong opinions. Keep asking why what inspires you, inspires you. Try re-creating aesthetics that catch you, so you better understand how it was made and ways you could riff off it. Keep your eyes open and the wheels turning and your software knowledge up to date, and you'll find yourself a huge and continuous value add to any team.