I've been researching this recently.
All the advise seems to point to less red meat, more fresh fruit and vegetables, low sugar, low salt, cut back on processed foods. Clean eating basically.
I'm quite lazy and really can't stick to a diet unless I'm well prepared. Take a day a month where you can batch cook healthy meals from scratch and freeze them to eat as abd when.
Keep healthy snacks in and where possible get others in the home involved.
I've just joined the gym (again 😐) but rather than just plodding along I've tried new classes, worked with the instructor to develop a plan I enjoy and can do without it being too easy but while not being so difficult I feel unmotivated.
And remember why you're doing it. Keep your goal in mind. When you want to quite, think why you started.
Also, a cheat day shouldn't mean the end. It's just a day. Just carry on tomorrow. We could do with an enfo diet support group 😊