In rock climbing, going from one level of difficulty to another can be daunting. It can be equally daunting going from one type of climbing feature or climbing area to another. As an example, many experienced traditional climbers find bolt protected sport routes alarmingly physical, while many sport climbers find trad climbing scary. If you've just climbed indoors, just going outside may seem really scary. Transitions from inside to outside, from bolted to trad, or from trad to bolted, need to be sensitively managed. Usually that means dropping your grade. If you've only climbed inside and F6a + (5.10c) is your limit, then do not try F6a + s outside. Start with F4s and F5s (5.7 to 5.9) and work up.
If you're going from one level of difficulty to another, in the same climbing medium, probably the best way is to use grade pyramids. For instance, if you've climbed E1 (5.9 / 5.10) but want to move into E2 (solid 5.10), then ask yourself, "How many E1s have I climbed in the last six months?" If it's only one or two, then you have not really consolidated at the grade. Sure, you might get up an E2 and maybe an E3 but, unless you consolidate, ie climb more at each grade, you're likely to get cough out. Conversely, if you've climbed dozens of E1s and never tried an E2, you're likely to stagnate.
There's no rock climbing law about this, but I'll take as a rule of thumb doing at least six routes at a given grade for 'mild consolidation'. So, if you've climbed 6 E1s recently, all onsight (without falls) and you're feeling confident, why not try an E2? If you're not confident, maybe do 10 E1s. But then ask yourself, "What's stopping me? Is it fear of the unknown? Is it my confidence? Is it my technique? Is it power, power-endurance, endurance?"
You could throw a rope down an E2 and top-rope it. You could abseil down one and have a look. You could just try a well protected one and see what happens. If you get up it OK, then why not try another? Why not aim to consolidate at E2 now, rather than E1, by climbing six or eight or 10 routes at the new grade. Then you may feel ready for E3.
So let's imagine you've built up a 'grade pyramid' of 15 E1s, 10 E2s and 6 E3s. Do you feel ready for E4? Maybe – maybe not. Only you can decide. But you've built up consistency and you will have built up confidence. You will be in a much better position than a climber contemplating his first E4, when he's only done two E1s, one E2 and one E3. Your solidity of experience will protect you from those 'rogue' routes that lurk at all grades for the unwary.
With sport climbing, grade pyramids are usually easier to arrange. You may have done 20 F6bs (5.10d), 15 F6b + s (5.11a), 10 F6cs (5.11b) and five F6c + s (5.11c). Are you ready for your first F7a (5.11d)? Maybe, maybe not. But again, your grade pyramid puts you in a far better position than the guy who's just done two F6bs and one F6c.
In climbing, sometimes we made big advances and sometimes we progress by incremental gains. Grade pyramids are a fantastic way of proceeding by incremental gains and getting us through those grade ceilings that appear so daunting in advance and so harmless in retrospect.