They are all great sources Augustin! Absolutely!

I recommend looking more into Simon Sineks research, into the Japanese term "Ikigai" and Martin Seligmans research on Optimism.

But, the more you generally learn about self-improvement, success and happiness, the more you see an underlying theme:

Action creates happiness. If you stand 100% behind those actions (if you give your all to as many things as you can in your day, from washing the dishes to the presentation at work and everything inbetween) you will be far happier.

It's a very basic overview but ultimately its about continuously creating something, never stopping and always finding new goals as excuses to go on more journeys.