I would like to know the meaning of this proverb (optimist:person who travels on nothing from nowhere to happiness)
If you are walking on nothing and go from nowhere to happiness basically means that you have an inner ability to go from darkness into the light without any problem with the transition. This being said, it implies that perhaps you do not tend to stop and look around to realize that something is wrong. Instead, you immediately find what is right and bright about things. A typical person would go through a period of grief, loss, or mourning when things go wrong, and then fight hard until they find happiness again. Some people may not have to do as much. They wait for the best to happen, without flinching. That, eventually, is the healthier way to live.
I'm afraid Voltaire would disagree with this quote. In his Candide, he portrays the optimist Pangloss as the consummate idiot. Satirically, he may agree that the optimist travels on nothing,-- nothing in his head---to nowhere with happiness. As Henry Kissinger said of Former President Jimmy Carter, "If you don't know where you are going, any road will take you there." The optimist wears tinted glasses; he cannot see reality. If this myopia leads to happiness, then, as Voltaire contends, there are indeed many roving idiots. At the very least, they are not realistic.
I believe the meaning is that an optimist is someone who doesn't need a specific reason, cause, or goal to be happy. Being happy is the goal, and is ultimately more important than anything else. Hence, place (nowhere) and objects (nothing) are irrelevant to the final destination which is a happy one.
If a person starts out at "nowhere," most people would say that this person is starting from an undesirable location that possibly is not only lacking in immediate appeal but that is also isolated from any place that might be more appealing. Traveling on "nothing" suggests that getting away from "nowhere" involves lots of hard work, unaided by anything that makes travel easier - no car, no paved road, no map, no GPS, nothing. To be able to start from a place that is completely lacking any redeeming features, which would cause many people to feel rather hopeless and helpless, and to survive all the hardships involved in getting out of that emptiness to a place of "happiness" - that is truly an example of an "optimist" - "one who usually expects a favorable outcome." A person willing to undertake that kind of commitment under those circumstances must be hoping for a positive result.