So, you've put in the mileage grinding at your craft and networking professional circles enough to land yourself a steady creative gig. Congratulations! Ok, now what? Like any relationship worth keeping, you are going to have to put in effort to maintain affection when times are sour. 40+ hours per week is too much time to spend doing something you absolutely hate, and since no job is always 100% perfect (unless it is, then good for you) you might have to put in a little extra self work to keep a healthy attitude about your job work. More importantly, these days job security frankly doesn't exist, and even less so as a creative.
There are many reasons that designers should never rely on job security depending on the field. For example, I've seen apparel company execs think that nixing their entire design squad and rehiring new people (or licensing out divisions) is the solution to giving the brand a "fresh" direction. Unless the team really wasn't doing a good job, this cut-throat corporate attitude only decreases overall moral and increases the likelihood that other quality people will loose faith in dedicating their careers and efforts to the company. Even if you are lucky enough to work for a company that's lead by smart, good people who know what they're doing and know how to humbly show their appreciation for the people shoveling coal in the furnace, don't make the mistake of getting too comfortable. Companies fold all the time for many reasons like not being able to adapt to market changes and even though you may kill it at your job, before you start asking "who moved my cheese?" know that there are forces beyond your control that only guarantee that nothing is guaranteed.
As an artist, the only work you will find that rides or dies with your soul are the projects you dictate yourself: The curiosities you explore, the visions you chase, and the freedom that comes with thinking as big and as out of the box as your mind and heart allows. However, we all compromise those ideals to some degree for that steady cash flow. At best, you get to work on some cool projects that are either fun and/or beef up your portfolio. At worst, the work becomes mundane, repetitive, stuffy, and restrictive to the point where your soul starts to slip away. Sitting in a chair for 8 hours a day alone can induce a kind of fatigue far worse than working manual labor (I have worked manual labor) - top that with fluorescent lighting stabbing your eyes and any excitement you had for the job is toast. You might work for a company that knows how to manage creative people effectively without suffocating their potential and encourage the exploration of personal projects (or better yet - provide the platform for doing so), but if not - how does one cope with the mundane aspects of a 9-5 and see it for something more than a paycheck?
Be a badass at your job and worry about impressing yourself FIRST. Set high standards for yourself with yourself and it will naturally radiate to others. (If you work with absolutely intolerable people, then analyze the pros and cons of your job and figure out if it's worth spending the majority of your waking hours in the first place.) Every time you get handed something easy, refine your process and focus on improving efficiency. When something more difficult comes your way, pave new ground and embrace the challenge of finding the best solutions. By challenging yourself, you stay engaged, present, on point with your job, and two steps ahead.
Document your work and constantly keep your portfolio updated with all of your best work. The more projects you work on, the more you have to choose from and edit. Know how to showcase that work in it's best way: Client logo, bulletpoint involvement/role, have good photography showcasing either the brand or your work, and an intuitive website. Even if your website isn't fancy, it has to be intuitive and easy to maneuver.
Stay informed with digital trends and how they influence cultural evolution (& visa vera). For every year you fall behind on technology trends and updates, you could fall decades behind without realizing it. The digital scape is growing exponentially and it's important to keep up with it's pulse to know what's going on. Read blogs, articles, see what's being talked about with regards to the way technology relates to lifestyle, the economy, and also how the tools of creation we have available are growing and what's to come. The effect digital tools have on our culture is exponential. Not only is infinite information available at our fingertips but having foresight into which products are going to be valuable and important to the market - and why - will keep you ahead of the curve. Also, knowing how to communicate effectively is a key component to being a good designer.
Keeping a good attitude can be a constant struggle but do whatever it takes for you to have the ability to find your "zen" at any given moment. Shit can get cray, especially under stress and pressure but there is something to be said for being that person who can keep the mood light and ease tensions (without being a clown). No doubt that when pinned between the crossfire of tight deadlines and bearing the brunt of ineffective management decisions, it takes every ounce of strength possible to not spontaneously combust but putting things in perspective is key to keeping chill. Keep it positive and focused on the project at hand. If someone is being a dick, take a mental note of what you're dealing with but resist the urge to feed into it. As time passes, all of that crap fades away and you are left with the fruits of your labor, however simple or grand they might be.
Each job is an opportunity for you to add feathers to your cap, keep things moving and watch yourself grow as new opportunities present themselves. Ride the wave while things are good and maintain the strength of will to not get sucked into a company's politics. If shit hits the fan, you're already prepared to make your next move.