"not forsaking". Forsaking (Gr. egkataleipo) does not mean to 'miss' as in 'miss a meeting'.
It means to forsake, leave behind, give up on, desert.
What Paul is saying is not to 'turn your back entirely' on the gathering of yourselves together.
It has nothing to do with missing the occasional meeting, since it's as much a state of mind.
You could be away from the meeting ill, but you have not forsaken the meetings because you still desire to be there.
But this true definition really doesn't help with guilting people to keep attending, so that's no good!
Splash.