OK if you have been waiting all year for January to come so you can make changes I'm not suggesting you decide to put it off for longer, go for it! However I have a theory why our good intentions fail at this time of year and why you might not want to be so hard on yourself if you don't make it past a couple of weeks. Making changes in January can be an uphill struggle.
Many people set January 1st as the start of their diet and/or new fitness regime. Unfortunately all those sugary and salty snacks are usually still around so if you've got unopened boxes get them out of the house - most supermarkets have donation points for charity where you can take them so you are not throwing away good food. However you might find that this is futile as quite often your work colleagues will use the place of work as somewhere to off load their goodies so they aren't tempted on their own diets.
Perhaps it is an addiction you want to kick? Smoking, drinking, sugar etc. So you've set up January as your 'will do' month. You've probably been doing more of whatever it is you want to stop over the last few weeks, particularly if it is something you do socially so it is now harder to stop because there is more of what you are addicted to in your system. If you have the will power to go 'cold turkey' then don't let me stop you but if you have tried at this time of year and always fail, maybe now is not the best time.
There are lots of websites with information to support you on whatever you are working on so do some research - particularly with addictions - and get professional help if you need to however you might find the following a comfort if you never make it to February with your plans.
If we look at the energy of wintertime, it is about withdrawal, it is a time for inner reflection rather than outer action. The weather is often cold and dark (although as I write this it is one of those glorious cold but sunny days) and the days are short. The yule time/Christmas (or whatever your celebration is during the winter months) provides a relief from the cold weather to bring people together and to brighten up the dark months.
It is therefore no wonder that we struggle to make changes because the season is not about change. So if you fail, don't be hard on yourself, try again in the spring when there is an outward shift in the energy of the season. Spring is the time for renewal and growth so you might find that working with the natural energy supports you rather than works against you. Also, you should have finished all your festive goodies by then and had time to slowly reduce your intake of addictive substances if 'cold turkey' is not your thing.
Final point - this is not intended as a reason to procrastinate. If you want to change something why wait? But as it is January don't be too hard on yourself if it doesn't work out first time around - you haven't failed until you stop trying.