Do you get enough exercise? The more you get, the more energy you'll have. There's nothing like feeling you can't drag yourself out for a walk, but doing it anyway - once you get your metabolism going properly, you feel like you could conquer the world!
I used to take my little one out in the pushchair to the park furthest away from us, so I could walk at a faster pace there and back, and we'd both get some fresh air and exercise. A bit of blowing away the cobwebs always made me feel tons better! xx