"Do what makes you happy" is right up there with "Be passionate" in terms of popular mantras. Maybe you've even said it yourself or posted it on your social channels with some type of ubiquitous cat poster. But can I talk to you for a minute on why you might want to take a step back from this one?
Are you happy or just trusting what doesn't suck?
The familiarity principle, also known as the mere exposure principle, basically says that, as we experience things over and over, we can start to prefer them. From the scientific perspective, this probably happens simply because it's more efficient for our brains to use well-worn neural pathways than to carve out entirely new ones.
So the problem is, when most people try to "do what makes them happy", they often end up leaning on what they already know or have learned. They can have a warped perception of how much joy they're really experiencing, simply because they haven't engaged in other activities that might be significantly more pleasurable and, subsequently, have no good comparative reference. They're not really finding new sources of joy or growing. They're just trusting what they know doesn't suck in an effort to avoid subconsciously anticipated stress.
So what should you be doing?
While your brain might like what it knows from an efficiency standpoint, from the mood perspective, your noodle eventually is going to revolt against you pressing repeat. It's when you do something new, something novel, that the brain's reward system jolts you with chemicals like dopamine that make you feel really awesome. It's when you push yourself and explore, when you learn more about who you really are or what you're capable of, that you get excited about yourself and everything else the world has yet to show you. That's when you feel your most creative, motivated and powerful. That's when life has its most vibrant color.
So don't "do what makes you happy" and retreat into routine. For real euphoria, you have to break the pattern. You have to do what's out of your comfort zone, to do what initially makes you a little nervous. It's OK not to stay in the same company for 30 years. It's OK to choose a cream sauce instead of the vinaigrette or read Dickens instead of Brooks, Hill or Carnegie. Do what you've never experienced and maybe, just maybe, you'll end up without any regrets.