Forget the word "diet" for starters. The very word implies denial and restriction. Say the word diet and the first thing that you think of is food and what you are NOT supposed to eat.
Then of course you want it!
A whole multi million £££ industry has built up around setting you up to fail.
If you need to go to a slimming club to motivate you, you will yo-yo all your life.
Unless you have medical condition it really is as simple as eat less, move more, so why pay someone to tell you that?
Start by reducing your portions but no food is a "sin" (that gives me the rage)
Every time you put something in your mouth, literally say out loud "do I need or want this" and recognise the difference.
If you are genuinely hungry have a couple of mouthfuls but don't eat that whole bag of crisps or glass of wine.
Waiting for the food you have consumed to hit your stomach before you have any more really does work, so eat slowly.
Always leave some on your plate, you don't have to finish it all just because it is there.
Of course these are just all things that worked for me having been overweight for most of my adult life.
I lost over 7 stone doing the above and have stayed that way for 15 years.
It does become second nature with time, you eat to live, not live to eat.
Good luck!