The 8 of Pentacles is about keeping up the hard work you're doing, and trying to be happy about doing that work at the same time. While the 3 of Pentacles is about completing a masterpiece, the 8 of Pentacles is about doing the apprentice work that makes you a master of your trade.
Even though everyone gets tempted to just abandon their sometimes boring hard work in search of adventure, now is not the time for you to seek adventure. You'll reap rewards you might not even realize from this hard work, when it's done.
The work you're doing at the moment has become boring to you, as a lot of work often becomes to anyone. You may feel an urge to let your project slide and focus on something new. Consider what you'll gain if you'd complete the boring work, though, before abandoning it or letting what you've accomplished so far degrade by a period of stagnation.
Don't turn your work or project into a prison. A brief period of laziness might serve to bring your attention to new opportunities, related to your project or not.