There's no magic trick to getting motivation. You just have to do it. I made working out a habit. I get up every morning around 4:30 and workout before the kids wake up. My husband goes to the gym. He comes home, and he, our youngest and I are out the ddor by 7:00-7:15. I just "made" myself do it, and it became a habit.
There will always be excuses. Find a time that works for you and stick with it. After 2 weeks, it will start to become second nature, just another part of your day. I'm not saying I'm amazing or anything, but I have a three year old and an 11 year old. I work full time outside the home, I do almost all the cooking, I do all the grocery shopping. My husband also works full time outside the home. He does all the laundry and the dishes. We tackle other household chores together. I take both kids to gymnastics, we all go to the 11 year old's basketball, etc., etc. I tell you this just to show that you're NOT too busy. There IS time. You just have to make it.
Temptation at work is hard, I know, my office has some sort of treat almost every week it seems. Just avoid it the best you can. If you can't account for it in your calories for the day and move on.