singlespeedscott wrote:With this training and your low body weight I think you’ll do fine.
With the wobbles on your descent try descending out of the saddle with your hands in the drops. Far more control and improved stability. Keep your legs and arms slightly bent to absorb any shock. Try to complete your braking before entering corners.
This is good advice. Not totally out of the saddle, but just a little bit. If you've already done a lot of riding in previous days, you'll probably be doing that out of the saddle thing for other reasons.
Always look through the corners if you aren't doing so already, that will help your descending a lot. If you are only looking just at what is immediately ahead of you, it's disorientating. And hands on the drops is not only getting your weight lower down (so you'll be more steady), it is also much safer on bumpy descents - on the hoods your hands can be knocked off the bars by a big bump. It's also a lot more comfortable, especially if you've got 20km of descent and a lot of big braking for corners.
The tip above on knees against the top tube is also good. I suspect some bikes are worse for these wobbles than others from my experiences.
To the OP directly, look at it also from another way, you had this happen now, not at L'Etape, you can do more descending and get more comfortable with it and find your way around this hurdle. You don't have to be a hero on the descents, just get down them safely. The more you do it, the more natural it will be. Good luck.