Pushing past the 3 week mark

I just recently started working out & eating healthier again. I have set the goal to loose weight every year for the last several years & never succeed. I've been fortunate to at least not GAIN any additional weight but am tired of being stuck at my current size. I have noticed from previous attempts that after three weeks is usually when I begin to struggle especially because I'm not seeing any progress. I want this more than ever now. Does any one have any good advice on how to push past that "3 week mark"? For those who have been successful in their weight loss, what are some of the things that worked for you to keep you motivated and focused on your goal?