Sometimes, no matter how solid your business plan, no matter how optimised for success your mindset may be or how thoroughly planned out your business' growth is, things just don't go the way you'd planned.
You may have created a surefire way to create steady income with your business idea based on the bare minimum of clients but if you can't actually attract a single client and you're coming to a point where the struggle is becoming exceptionally hard and upsetting, it's time for a change in direction.
You can never fail until you have exhausted every single possible (and sometimes, impossible) option. You cannot truly say you tried your best until there is nothing left for you to try.
Sometimes, it's merely a shift in pricing or market targeting that can realign your strategy and get you back on track with that minimum number of clients. Sometimes that price adjustment is actually higher because your target market thought you were suspiciously too cheap before.
Whatever the shift, look at every reason why you may not be succeeding. Look at your marketing metrics, look at how you're serving your client base, how you're recruiting it, what you're charging, what you're doing right and what you may be doing wrong. It's time to analyse and look for creative ways to cause positive change.
You are not failing. You have not failed. You haven't exhausted your options yet. Keep going.