”Action may not always bring happiness; but there is no happiness without action.”- Benjamin Disraeli.
There is a level of adrenaline that runs through the veins of a man in action. An inactive man will just remain calm and docile because the bodies will just stay relaxed.
Action breeds happiness and a man with work to do will always have something to be happy about.
Working doesn't mean you have it all, or will it guarantee you do not need to struggle, but you get some level of excitement that will give you something to live for.
You can be as happy as the feelings your life and its activities gives you.