Honestly rating your own skill level is a very crucial safety skill. In addition, this is a moving target. When you first start boating, many find their skills rapidly advance. This is quite understandable in class I/II whitewater. The next jump to class III is a big one. Most of us remember our first trip down the Lower Yough - my gold standard for class III rivers. It's one thing to run a single class III rapid on the Lower Gunpowder, Robin's Nest on the North Branch, or perhaps Snap Falls on Muddy Creek. It's a whole different ball game running a complete class III run. Rapids are very continuous, swims are much longer, and manuevering is absoutely essential. This can be a dangerous time for new boaters. They might have a solid roll but lack adequate boat handling skills. They see their friends running more challenging rivers and may be easily lured into rapids above their present skill level. This is where good judgement is crucial - know when to say no.
The seasoned paddler that hasn't gotten out much is another accident waiting to happen. You used to run class V rapids with ease. Perhaps you took a few years off raising the kids. Work may have kept you from paddling regularly and you hardly get any exercise. Do you really think it is wise to start off the season with a run down the Upper Yough? Paddling is not like riding a bicycle, it takes practice and has more serious consequences for the unprepared.
Stepping It Up - The Safe Way
Find local runs you are quite comfortable on and really work them. Most solid class II+ runs have class III (and sometimes class IV) manuevers. Practice back ferries, attainment, slalom gates, and surfing. Practice your roll in moving water. Give playboating a try. Paddle with strong boaters and have them test you on these easier runs. All of these tactics will greatly improve your boating skills and make stepping up to the next level much easier and safer.
Training with an instructor can also help. Most clubs run very inexpensive classes at many different levels. There are also a large number of commercial schools. The Cheat Race Training package by Tom McKewan of Liquid Adventurers is a unique bargain even if you choose not to race. Get references on specific instructors from people you trust - World class paddlers don't necessarily make the best instructors. get someone that fits your unique style of learning and make certain you have a reasonable student to teacher ratio.
Variety is essential as well. Just because you bumbled down the Lower Yough following someone's tail - doesn't mean you are a solid class III boater. Paddle a variety of rivers in your skill range - each have their own learning opportunities. Build big water and technical skills. Try your hand on fun races. I also highly recommend taking turns as the river scout and leading trips. Offering to lead trips provides great learning opportunities and will certainly get you recognition from more seasoned paddlers. We have seen plenty of boaters that blindly follow the back of someone's PFD down the river - that isn't boating. What if your lead catches a one-boat eddy? Can you read and run on your own? Can you quickly identify and catch small mid-stream eddies? If you can't, you really need to build your skills before tackling tougher runs. Here is a nice short article on judgment I wrote with additional references: Judgment.