Correcting Bad Posture?

Hey FB community! I've noticed that I unfortunately suffer a bit from 'Daffy Duck' syndrome in my back (if you know what I mean you know what I mean)... Does anyone know any corrective exercises to straighten my back and make my posture better? I remember hearing that it's down to hip flexor flexibility, and mine are notoriously tight, so it might be that. Having good posture makes me feel stronger!

Also, anyone have any advice to doing flexibility workouts consistently? For some reason, I can't seem to stick to them like regular workouts, even though I'd really like to improve in that area. Thanks!!