I have always thought about this and here is my conclusion
Money is very important element to be happy. There are others like social life ( family, relatives and friends ), health, ...etc. The 7 habits book explains these elements very well. If there is a lack in any of them you will feel unhappy to some extents. The bigger the problem in any of the elements, the more unhappy you will be. Someone getting divorced isn't like someone had a fight. Someone has a cold flu isn't like someone has a Cancer..etc. So, you need to balance all the elements as much as you can to stay happy.
Now, about money itself it can affect your life extremely. Like earning 100$ a month and not being able to support my family will make my life like a hell. While earning 10K per month will provide me with great lifestyle. There is a point when money doesn't matter. I don't think someone earning 100K per month has a different lifestyle than someone earning 1 Million.
Hence, money is a mean, not an end. Money in itself doesn't hold a value. The value in using it to secure yourself and your family. As long as you have enough money to do that then its better to focus on something else or another element like spending more time with your children.
I feel really sorry for those who spend their time gathering a lot of money. And they have a damaged family or don't have family at all.
I am not talking nonsense or making conclusions. I left many opportunities to make huge amounts of money cuz I found it will take time more than I am willing to give. If I am earning enough to provide my family with good lifestyle, I rather spend my time with them than gathering more and more money.
Fancy Cars, Big Houses, Women ...etc. Read the forum, all the people I know when they made their first big cash they tried it all. Now, although they are making more, they are okay with having nice house, 1 good car (not super car), travel once or twice a year and that is it. When you try shiny stuff, you will know it's not really like it seems.
So, my conclusion, Money is very important, but it's not the most important key to happiness.