hales the therapist recommended this tip for encouraging good behaviour and I find it works really well. When DC does something good you praise them, but only a little "well done, good job wearing your glasses today/this morning/ while we were doing x activity"
then you tell DH or someone later in the day:
"DC wore their glasses while we did x. They kept them on the whole time and were really good"
So then DH/gran or whoever says "oooohhhhh well done DC, that's really good"
Basically the kid joins up the dots that you all think they're great when they do something good. Without too much direct praise, which they can forget quickly and easily.
Obviously you would use whatever language and reaction you naturally use. It's just gentle reminders for them of good behaviour. I always notice when I do this with DS that he listens quite intently to what I'm telling DH.
I hope that makes sense. It's a marathon, not a sprint!.... Sadly 