Update---
It only appears to be true that two incomes are often required to "survive" in today's world, when we were faced with the same issue (after MUCH thought and procrastination) we chose to rearrange our whole lifestyle to accommodate a one income household. All situations are different but I have a strong need to oversee our children as they grow up so we agreed I would quit my job, cut our income in half, we moved, got one cheaper car and to be completely honest we are all much happier now. I had an interesting childhood that has allowed me to know what its like to be the "rich kid" as well as "the poor kid". Speaking from experience I learned significantly more beneficial life lessons while I was "the poor kid" and there is only shame in it if you choose to see it that way. After all the definition of "poor" is variable. To a billionaire all of us are "poor" and to my 6yo he's "RICH" with a few cents in his pocket. We do live in a country where status gets respect but it really is impossible to keep up with the Jones's and trying won't make anybody happy. We all know money doesn't buy happiness but I can guarantee you spending quality time with loved ones will. Your children are only young once and you only get a few short years to share, play, teach, love, guide, praise, listen, help them reach their full potential. Every single one of us wants to be the best parent we can but its easy to forget that it's not our peers that give us as moms that stamp of approval and in our old age we realize the status of our lifestyle was never relevant to begin with, the stamp of approval that will matter to you in the end can only come from your children after they become adults. End of update---
I'm sure you know children can see when you are stressed, tired, upset or whatever and it does effect their behavior. First of all set aside a few minutes for yourself each day after work and before going home to wind down a bit. You could take a quick jog around the block, have a notebook in your car to write out any vent sessions from work stress, specialist say a power nap of 20 minutes (no longer or shorter) gives you enough time to relax without falling asleep. Of course that's assuming you get 8-10 hours of sleep each night and if you don't changing that alone will do wonders for you.
Ideas...
1. Set aside a time shortly after you and your children get home each evening to hear ALL about their day and even though you are all tired make sure to take great interest in what they have to say.
2. Eat dinner together at the table every evening, you could even use this time to hear about each other's days.
3. Think of some special and gentle way to wake your children each morning. My grandma use to bring me a glass of orange juice in bed each morning. Man I loved her for that, she's 96 now.
4. You and your husband swap reading a story or two to your children every night, you and daughter one night and you and son the next.
5. Get one of those food coloring/icing pens and write a message or draw a picture on a sweet portion of their breakfast. My grandma had an iron stamp for toast that said, "Mornin' Darlin'".
6. Get some of those cheap little cards available in in the gift wrap isle at walmart or target and write little notes or pictures to them. Hide them in places.
7. Have some sort of fun activity you do each evening to bond. Let them finger paint one evening and take a nature walk the next. Let them help you make an easy portion of dinner like pigs in a blanket or something. Teach them how to make homemade ice cream. Scrapbook with your daughter, I don't mean the expensive way its just the time that counts.
8. Take them to a new park in the city on a certain evening each week and maybe even pack a picnick or snack.
9. Help your daughter cut pictures out of a magazine that she likes and paste them to cardboard.
10. Teach them how to play a new game.
11. If you have a video camera let them make a video.
12. Color, draw, or pretend with them.
13. Get one of those craft books and always have some sort of family craft in the making.
14. Get down and roll around on the floor with them.
15. Play house with your daughter and let her be the mom if she wants and be a good daughter for her.