The virtuous person is the happy person. But we can’t say that without having to think about the role of luck.
A more virtuous person is a luckier person, first off. This is not because of karma or even providence exactly, but because the cumulative effects of your actions push in a good direction and dispose your situation to be better in all sorts of ways.
But even if good things happen to you more often as a good person, that doesn’t mean nothing bad ever happens. Bad things happen to good people, as everyone has always known. On occasion, the worst things happen to perfectly good people.
And vice versa. Even if an immoral person will generally speaking end up meeting with bad luck more often, there are many examples of bad people who ended up getting very fortunate in one way or another.
The simplest and classic way of dealing with this problem is to look at what happens after death, at final judgement or reincarnation, where the scales are balanced.
There’s a long tradition, though, of limiting the scope of our musings and saying, is it still worthwhile to be virtuous, from the standpoint of happiness in the present life alone, if all our effort can be cancelled out by a single bad roll of the cosmic dice?
And the answer is yes. Good luck and bad can befall the virtuous and the vicious alike. The good person who suffers a great misfortune will admittedly not be as happy as if the bad thing never happened. However: the virtuous person who suffers evils will be the happiest it is possible to be while suffering what could happen to anyone. Conversely, the bad person who enjoys a stroke of good luck will be the most unhappy it is possible to be while enjoying what could have happened for anyone.
It just makes sense. The most important thing you can do for your happiness, no matter what is coming, is to pursue virtue ceaselessly.