Pleasure is that which motivates you to continue experiencing it.

Note that there is a difference between finding something good/positive, and
deriving pleasure from it.  When you call something pleasurable, you state,
implicitly, that you want it to continue _because_ it causes you pleasure; you
do not care about _what_ is causing the pleasure.  When you call something
good, you are making a value judgment; you imply that you care about _what_ is
good.