If you are struggling to get started you may need to decide you are going to have a say a month of healthy living. It is something like that time period to establish a habit. After that extend it to a year.
You then need to avoid your points in the day/week/month when you slip. That might mean eating or drinking bad stuff between meals so swap that for no more than a piece of fruit or water between meals.
It may mean what you are having at meal time so do something easy and calorie count and track using a phone app. Try out some new meals.
Motivate yourself by reading up about healthy stuff. Have a goal by when you want to have lost a couple of pounds then go on from there but in small amounts.
Have a month of saying no to social snacking e.g. if someone offers you cake and a latte just have a plain coffee or tea or better still water.
Then try to build in more activity as that makes you feel better and keeps your motivation higher. Commit to exercise and schedule in when it will happen especially if it is at times of the day when you might otherwise eat between meals.
Ultimately you have to get through the first month, so even if you get out of one bad habit, before you crack on with a diet, you will be in better shape going forward.