In reply to Zen:
It's natural that the pace of grade increase slows as the routes get harder.
- Generally the harder the route, the fewer the number of ways there are to do that route so each route takes a little bit more time to figure out.
- Harder routes tend to become more specific. For example a 'crimpy' 6b and a 'crimpy' 7b will be totally different animals... the former being a jug fest with a few crimps ... the latter being a crimp fest with a few jugs. If you've not got the specific skills (be that crimping, jamming, smearing and so on) you'll struggle.
My advice? Just keep climbing and keep trying harder lines. Eventually you'll break through. To climb 7a you don't really need to do any specific training ... climbing lots is enough. You'll get there.
The next big milestone from there is 7b+ which is a world away from 7a again. This will require a fair bit of dedication... maybe some power endurance training as most 7b+s tend to be long.
From there... 8a. For me at least... I had to train for this... campus, finger boards, core strength and good fitness were key.