How to prevent multiple pages on the same topic / keywords from competing with each other in serps?

I'm building a new site and am wondering about structure and how to prevent related keywords from competing with each other in the serps?
I have 6 topics I'd like to rank for, each topic has about a dozen related kws (that I'd also like to rank for).
Let's say these are my kws:
Happiness (= topic)
How to eat for happiness
Happiness coach
Happiness supplements
Happiness online program
...

- Wouldn't they all compete for the term happiness? Is this an issue? How do I prevent this?
- Does it make more sense to write 1 really long article targeting all the kws?
- If not, how do I structure my site for optimal serp performance?