One way to try and keep your motivation going is to set a challenge for yourself. You can do this alone or with other people, and first try it with setting time limits so it doesn't feel like such a big thing (i.e. I'll start taking the stairs forever vs. I'll take the stairs at work for the next 5 days).
Challenges I've heard lately:
- going to the gym twice in one week
- walking up and down the stairs at work instead of taking the elevator
- preparing produce and having it available in the fridge for a pre-dinner snack
- eating 25 types of produce in one week
- not eating after 9pm
- walking for 10 minutes at lunch time
- only eating prepared foods that have 5 ingredients or less
- not checking email after 10pm
- doing one exercise video on the weekend
Pick something that makes sense and is reasonable for you and your lifestyle. Make it interesting (and rewards can be helpful too!).