The problem with a pleasure-based moral system is that it tends to be self-defeating. Addicts who accidentally overdose cut off the prerequisite (their own life) for experiencing pleasure and positive emotions.

That system tends to be other-destructive too. Wouldn't take long for those with criminal tendencies to overrun the rest of us if the only moral system we established was founded on pleasure and positive emotions (presuming, then, that law does not exist since the standard for morality is subjective).

Positive emotions are important to a good life, but your anecdotal evidence isn't enough to discount morality or the intellect as sources of value. Suppose someone had an aesthetic experience, or something analogous to what you had, while contemplating a moral or intellectual theory?