the only person who can change you is you, instead of simply thinking the worst, try following that thought with ...if that happens what will i do ....and work out a solution so the positive can still be possible e.g you need to go to the supermarket to get something for supper, the worst that can happen is you don't get to there because the bus doesn't turn up, ok it didn't turn out as planned, so what can you do to make the positive happen? you could wait for the next bus, walk or cycle to the supermarket, you could go to the corner shop and get something from there and try again tomorrow, or you could go home and invent a new dish from things you have in, so whichever you chose to do you still achieved getting supper!
I always have to plan for the unseen, very often i plan to do something and have to rearrange my plans because my health gets on the way, but i am always ready with a so what now!
there's always a way but no one way is ever the only right way.