Being self employed is good if you truly understand you ARE your business. You pretty much have to live, sleep and breathe your business (unless you have alot of the responsibilities delegated, and even then there are certain executive functions you always must perform to keep the business running smoothly)
It depends on the field, really.
You obviously have to be comfortable enough to know what you're doing in your field order to be self employed. You also have to be a natural leader(if you have employees) and treat your employees like family.
More importantly, you need the resources and connections in order to be on your own. If you're not at that point a related job in the industry will help you establish those. Eventually you hit the ceiling and realize "hrmm...i do pretty much everything for this business yet im making someone else richer".
there is great reward, but also great risk
the flexibility is great, but the responsibility is considerable. discipline is very very very important