Hi Sadie,
It's all about making small, progressive changes over time; build those 'good' habits, and make them stick.
Having to control and restrict what you eat is really hard; eating is such a natural, pleasurable activity. But don't despair, there are so many foods diabetics can eat (healthily)that are delicious, it takes a lot of effort at times, but it's worth it for the sake of your long term health.
Regarding appetite, I would recommend doing some research on satiety(food fullness factor), certain foods e.g
proteins (chicken breast, etc), monosatuared fats (avocados, pistachios, cashews) and veggies (love/hate for me, but keep me full) are superb at curbing hunger.
here's a link to start you off;
http://www.nutrition.org.uk/healthy...anding-satiety-feeling-full-after-a-meal.html
The mental/emotional health aspect is totally linked to control, I've been diabetic for 20 years, the periods where my control was poor affected my emotions/outlook a lot. When my diabetes is under control, I feel normal/amazing.