Don't fight it! Winter is nature's way of making us take a break from routine riding, and that's good. Get back in the pool, join an adult soccer league, signup for yoga, get in the rock climbing gym etc. I'm never surprised that the guys or gals that JUST ride and couldn't do a chin-up to save their lives, are the ones that get complicated compound fractures and disclocations when they crash.
Anything can get boring without some variety. So your overall approach in the off-season is to reduce saddle time and give those pelvic floor muscles a rest.
The principles of training:
Specificity: Your training program needs to be tailored to you. The majority of training books give you a stock program to follow. It will be down to you to tune this to yourself. When doing so you need to be realistic, asking yourself the following: What is my current level? What training can my body realistically cope with? What time do I have to train? What are my goals for the following year? When are those goals? Once you know the answer to these questions you will have the information to make a realistic training program. If you work 40 hour weeks you cannot get 25 hours in on the bike. If you are new to cycling and not very fit, then you cannot physically cope with the demands of a six hour ride at 20 miles per hour. By tailoring your training to you, you will have a program which you can fulfil and by doing so will be more motivated to follow.
Overload: Like the body builder doing very few reps with an enormous weight, the principle of overloading your body to make it improve is relevant to winter training also. By placing a higher demand on your body than it is used to (but one which is realistic to achieve) your body is given a stimulus to react to. By riding longer than you normally do, or at a higher rate, you stress the systems of your body. We are programmed to adapt to these changes and thus get fitter. Though note, it is only during resting that the body can improve. Training is a two part process, stimulus and recovery, one without the other will not achieve an improvement in your fitness.
Progression: As we noted above, our bodies adapt to the new demands placed upon it. This means that as you train and get fitter you need to progress your training. Increase the work load which you put your body under. If you only ever do the same about of training then you will plateau. So as you get fitter you need to increase your training, in either length or intensity, to continue to improve.
Reversibility: This is the least favourite of all the training principles. Going hand in hand with the body’s ability to adapt to new demands put upon it, when those demands are not present then it reverts back to a normal state. In layman’s terms you lose fitness when you do not train, very quickly. With this in mind it makes sense to be consistent in your training, little and often. This will limit the losses during down periods, or when you are limited for time to train.