There is nothing to be gained in making yourself happy.
Strongly proven to be untrue, that statement. Happy people pretty strongly tend to be more effective at what they do, whatever that is. More energy, more alertness, etc., so forth, so on. Happiness is good for the brain and body, more or less. Does not, of course, mean that not-happy people can't be energetic, alert, effective, etc. -- just that they'd almost certainly be doing even better if they were happy, as well. Happiness is objectively optimal for the achievement of goals... unfortunately.
That said, one's job
is less to make yourself happy than it is to
do what you want to do. Happiness may or may not be involved -- there's plenty of other causes to dedicate yourself to, wholly or in part, for which happiness is a secondary concern at best.