Neurolinguistic programming (NLP) can be really helpful in re-framing thoughts from a negative to a positive. Thinking either positively or negatively is a habit that can be changed though conscious thought and practice.
I would recommend taking a look at some NLP stuff and see if you can apply any it with your kids. A good easy to read introductory book on NLP is Ultimate Power by Anthony Robbins, but there is also lots of good info online.
I'm the master of reframing negatives into positives now.. Drives people that want to look on the darker side of life crazy. Apparently it's one of my superpowers. The ability to see a silver lining anywhere, hehe.
Lokah Samastah Sukhino Bhavanto
'May everyone everywhere be happy
May the whole world be joyous'