The New Year is a time for new beginnings, new possibilities, improvements, growth and New Year's resolutions. These can be in every area in our life and not just in any one area.
Shoshin ni kaeru is translated as, "a return to a beginner's mind," or "going back to the beginning." No matter how long one has been training, it can be possible to become complacent, bored, frustrated, and self-satisfied, amongst other things. These can be possible on a physical, mental or spiritual level. These can often lead to one slowly but surely, or even suddenly, stopping training.
One should take the time to remember the excitement, enthusiasm and interest that one had when beginning training, along with the improvements and progress that one has made, no matter how long one has been training.
Going back to the mind of a beginner and going back to the beginning is mandatory to continue to learn, make progress, remain humble and to KEEP the mind of a beginner, no matter the length of one's training. The New Year is a great and very appropriate time to do this, hence it is indeed the New Year!
Happy New Year!