I think that a new year resolution to go on a diet is a mistake. You put too much pressure on yourself, don't loose your target poundage by March so drift back to bad eating habits. Why not be kind to yourself and just resolve to eat less?
Put away large dinner plates, use smaller ones.
A portion of meat or fish should be no bigger than half the size of your hand.
Eliminate processed foods, and cake and biscuits etc.
Exercise.
Some studies show that telling friends and family about your decision works, other studies say that keeping quiet and not sharing works!
If you need to shift a stone or three then Weight Watchers or Slimming World is probably the way to go.
Whatever your decision, I really hope you're able to stick with it and feel good again.