How much can a positive mind set work till reality sets in?

I have had some I would say crap luck of the late, but I have kept my head up and said fuck it not in the bad way but just keep going kind of way.

And there is that side of me that says you can still do it, but you know you have to look at things for what they are after awhile.

I guess what I’m getting at is how much can you say “I can” ” I won’t stop” etc…. Before you have to just accept that it ain’t gonna happen?

Where do you draw the line between your bullshitting yourself and just keeping your head up?