Preface to the following: I don't have enough time to frame my arguments in a more objective view-point, so, for those that read this post please do not take them personally! I respect individual free will greatly and never expound my philosophies unless someone asks :)
I would agree, in the end it is ultimately about happiness and joy. However, if you are inherently seeking personal evolution (which is what joy IS), 9 to 5 will do a lot to suppress that.
Unless you happen to be paid for research or bleeding edge development on some cool project, building webapps for other people day in and day out; or doing maintenance work day in and day out isn't a terribly creative expression IMHO. (Creativity IS spirit, it is an aspect of the intellect - there is regurgitation and then there is creativity)
I resigned from my 9 to 5 (as a systems engineer and web application developer) to pursue my self-education and a startup idea. While I almost did not hand in that letter of resignation, I did, and I am loving my life.
Mind you, I am 22, have 0 debts, 0 dependents, and am willing to live out of a tent and work from the library till my projects begin to generate an income (yes I am a lone wolf).
If you feel fear, that is an excellent indicator that you are staring right at your 'edge'. Edge being that boundary in which you, as a man (I'm assuming you're a man), find your present state of consciousness expanding into; pushing that edge pops the bubble and you begin expanding into that new boundary. The phallus is an excellent symbol, as men (speaking for myself and many that I know, I apologize for the sweeping generalization) we feel purposeless and mediocre when we are not constantly PUSHING, SPEARING, HUNTING, PENETRATING.
Find your edge and lean into it (don't jump off the edge), push push push. Use the masculine aspect of your psyche (intellect, hunter, etc...) to challenge yourself and your edge; you can even do this within the context of a 9 to 5 job, however, you will find at some point the typical 9 to 5 structure of serving your time to someone else is far less appealing than serving it to the greater self that is your life.