If the last half century's worth of research on positive psychology has taught us anything, it is this: You cultivate your perception. Your happiness is a choice. Rather, it is a series of choices you make to develop your mindset and lifestyle.
Logically, we can gather how worrying doesn't help anything, problems are never as bad as they seem, we'd be better off if we could just focus on gratitude, admit we have a problem, seek professional help, choose to view the glass as half full... and so on.
People reject the idea of "choosing happiness" because it seems impossible to just "choose a feeling." (It is.) Choosing happiness is assuming full responsibility for your life and making the moment-to-moment, day-to-day decisions that facilitate your well-being. Despite this being so simple, people still have a resistance to committing to themselves. Here, all the reasons you may be feeling as though "choosing happiness" is impossible, and how to dismantle them.
1. We are deeply convinced that nothing "good" can be easy. If we want a "good" life, we have to suffer for it. In fact, our minds operate so much within duality that when we identify what we want, we also identify what we don't, and so on. But this mindset is not irrevocable. We can consciously choose to acknowledge the opposite without entertaining it to the point of believing in it.
2. We think we'll stop growing. If we radically accept everything as it is, we think we're dooming ourselves to a homeostasis we've already determined to be "bad." The reality is that we never stop growing or changing; accepting who and how we are doesn't stop that, it makes it easier and more likely we make choices out of love and desire as opposed to fear and shame.
3. We believe that our pain is our safety. As long as we are being "realistic," we can't be surprised by any bad crap that comes along. We're programmed to think that being conscious of every possible way we are "less than" is self-awareness when in actuality, it's "projecting our insecurities as what we assume any given person would see in us and adopting that projected idea as our own." (Also, no amount of preparation can actually prepare us for suffering... but it can rob us of the happiness we do have.)
4. We believe that something else will save us. God and money and love and sex and romance and the new job and the new outfit and the next day and whatever else we can take and earn and grow and change. It's easier to dismiss the situation at hand and just hope for something, anything else, but eventually we spend our lives just wishing everything away (and completely missing out on the "good" that exists alongside the not-so-great. See: duality mind, as mentioned above.)
5. We were never taught how to healthfully process negative experiences, so we don't. We accept them as fact, rather than an interpretation of an experience we had, or something that served to reveal to us a limiting belief that we had to let go of. Simply: The good things are to be enjoyed; the hard things are to be learned from. Overall, the point is growth, and you achieve it either way... but you choose which way you go.
6. The only "happiness" we have ever put time and energy into cultivating... has been external. We've never had to truly awaken an inner feeling of joy, so we don't really know where to begin (or what it would even feel like). In the end, our essential, natural, peaceful state doesn't immediately feel as good as the alternative, but this is mostly just because we've never put time or energy into it before! We have to be open and ready to start small, and slow, and forsake instant gratification for once.
7. We don't want to have to rectify what we feel wasn't our fault in the first place. Life dealt us a shitty hand. Life should fix that. Because it isn't immediately apparent to us how our beliefs create our experience, we often seek a rationale, a greater purpose, other than our own path to awareness. This usually culminates in the belief that "bad shit just happens, and there's nothing we can do about it." In reality, we just can't be conscious of it beforehand to prepare -- there's always something we can do.
8. We don't realize that just because we can choose happiness, doesn't mean we must all the time. We can also choose to feel grief, to process having lost someone. We can feel sadness, if something hasn't worked out the way we wanted. We can feel pain, or envy, or joy, or melancholy, or just "okay," the point is that we realize we can shift our thoughts, and therefore our emotions; we can choose to process what we experience, rather than pack it away and suffer.
We choose every experience we have -- subconsciously or not. If you want proof, look around and see how great our propensity is to needlessly choose suffering and pain and worry. Nobody will hand you the key to liberating your mind. But most suffering stems from not realizing you were always in control.