Those 3 clients every month were the difference between being a work-at-home, solo business owning, entrepreneurial mum or going back to a "proper job." That plan created my business. I kept it on my desk, referred to it daily and added bits and pieces until I had something more structured, however for a long time that little page was it -- and it was all I needed.
A business plan has to be something you can work with, it should be a coffee stained, well thumbed, highlighted, annotated, and frequently corrected document. It is a work in progress, just like your business. It should be referred to regularly and adjusted according to your needs. Anyone who creates a business plan then sits it on a shelf and calls it done is making a big mistake and that mistake can cost them their business.
Your plan is your map and you can't follow it unless you look at it. Write your plan and use it daily, add to it, change stuff, make notes about what didn't work but most of all let it be your "bible" and it will guide you to business success.