I find that to be good motivation, actually. It's motivation to accomplish something and get some joy in the hear & now before it's over. It's motivation to enjoy the incredibly valuable, unlikely gift of ever having existed at all.
your statement is not logical, to believe things just because they make you happy would be delusional. Logical in this context would mean something that is reasoned out in a logic method, how happy something makes you feel is not a suitable or logical method.