On the whole, being ambitious and being happy are likely going to be in opposition to each other before the ambition is accomplished. A lot of things worthy of being described as ambitious are extremely hard by definition. There are likely to be many failures on the way. Perhaps years worth of failure. Perhaps someone's ambition will leave them crying themselves to sleep at night because they may never accomplish the goal and they hate that. Or perhaps their entire body is a mass of bruises or every muscle is sore because of how hard they are pushing their body.
Thank God we had ambitious people working to create vaccines, help feed the world, etc.
Helping people / the world survive better?
Why would people pursue noble, philosophical causes? Because it makes them happy to see those pursued. Why would somebody want the world around them to be better? Because it makes them happy to see the world be a better place. Why would somebody sacrifice of themselves to see a loved one better off? That's kind of the definition of love, that they're happy that their loved one is better off.
This gets more tautological than philosophical.
An example would be the parents in poor family working very hard day in and day out to ensure that their children go to college and secure future prosperity. That's just one example but you can think of countless different scenarios where people sacrifice a bit of their present to capture an ambitious future - or to make that present sacrifice in the name of ambition and future success.
I actually heard all of this in a video but I can't for the life of me remember who said it, and it was put infinitely better than my explanation. If I remember I will let you know!
