I am big proponent of taking risks as a way to succeed and way to learn. If you find yourself unable to overcome the fear of failure, try minimizing the cost of failure to give yourself that extra nudge.
The theory is very applicable to opening your own law practice or to making changes within your practice. If you are considering going solo, but cannot fathom having a variable (or no) income for six months, minimize that risk. Work out of your house to reduce overhead, spend a year saving up money to cover dry spells, or even consider working part-time somewhere to pull in steady income.
If you want to switch to a new practice area, make it a slow transition, and make a living off your old area while you transition. If you are interested in a new area, consider handling a case pro bono, or take a case through a local volunteer agency.
Minimizing the cost of failing is a way to shorten a cliff, and to make sure that you take that leap of faith.