The best way in my opinion to start fresh with your blog doesn’t mean deleting your previous work. Yes sometimes you have to start from scratch but perhaps a change in focus and content is all you need. Perhaps changing your theme can help make your blog look and feel new. I think taking a day off from posting anything can help reset things for those who follow you.
Don’t be afraid to experiment a little with your posts too. I always prefer original posts so see what others are posting about for ideas for your own site. Have a great year of blogging ahead my friends. Yes the new year is a great time to do new things here on Tumblr.