Besides taking into considerations all of the points above (weather, experience, location, etc...) a solo sailor needs to carry the proper safety equipment. You should really make the effort to have most, if not all of these items:
VHF Radio (in waterproof bag)
Cell phone (in waterproof bag)
GPS (Tell help where to come get you)
Knife (on lifevest)
Whistle (on lifevest)
Small first aid kit.
Light sticks
Anchor
Righting pole (helps conserve strength while righting)
Towing insurance
Flares
Duct tape
Towing rope

In the past few years we have seen sailors drown under sails and rigging and die from hypothermia while sitting on an overturned cat. You should always wear your lifevest while sailing solo. All of this gear can be purchased for under $500. a small price to pay for insurance if something goes bad.
Earlier this summer I had a dismasting while racing with our club. Although I was in protected water with other sailors I could have just as easily been out 5 miles in the gulf that day.
A little bit of preparation can save a lot of grief or prevent a tragedy.