Winter is without a doubt the most difficult time of year to train. Not only do you have limited hours of light and sometimes freezing cold weather but motivation is also hard to maintain! It’s easy to say “It’s raining I’m not training”, or “It’s too cold”.
#1 Motivation
Why not start here! For everyone it’s different, but I find goal setting the easiest way to maintain motivation, races certainly help with this. If there are no races then plan your training with a few swim, bike or run time-trials each month.