Yes you can. In fact, considering happiness is a feeling, it’s a reasonable question whether there is even a difference between feeling happy and “being” happy.
The difference is maybe analogous to laughing uncontrollably and imagining yourself laughing uncontrollably. Imagining yourself laughing uncontrollably can lead you to feel more ready to laugh, but it is not the same.
If you answer, well laughter is physical while pain is mental, then I will ask you how that is a genuine dichotomy. The mental representation of unexperienced pain is also, in truth, a physical phenomenon since the mind is a physical experience, but the mental representation of pain is not the same as experienced pain.
But pain or pleasure, sadness or happiness from some imagined event, yes, that's real and it's what the original sentence intended to say, I believe.
Edit: This was meant as a reply to addicted rather than foldr...
Imagining yourself feeling happy can lead to you really feeling happy, but imagined happiness is not the same as experienced happiness. You imagine being happy, and _then_ might put you in the right state of mind for actually experiencing happiness. Let's remember that also the mind is either a physical phenomenon or else it is a spiritual, supernatural one. I go for physical.
Indeed. Thinking happy thoughts can make us feel happy. All experience is colored by records of past experience. So bad shit reminds us of similar bad shit, in the past. And so the bad thoughts and feelings become self-reinforcing. By interrupting that, we can make ourselves happy. Or at least, stoically happy.
By the same logic, I can feel happy just by imagining myself feeling happy?