+1 for subcontracting for a larger consulting agency. Almost always, the stressful parts of a project revolve around the client relationship and overhead(time which is generally unbilled), and not around the actual work. If you go it alone you own all that. If you subcontract on a signed project you can skip this. On top of that you'll be part of a larger group all striving to get the job done for the client. This is great for two reasons. First, someone else will handle parts of the project you aren't skilled in. Second, if unforeseen circumstances arise that require you to leave the project, you won't leave the client high and dry.

If you can be a regular subcontractor for a larger agency, that IMO is generally the ideal situation.