Women need to de-stress just like men do. The problem is that for men, sex will release stress - so men want sex when they're stressed. Women want nothing to do with sex when they're stressed. Women need to be relaxed and have their head clear before the thought of sex even enters their minds. So create an environment where she can de-stress. Let her vent if she needs to - and then immerse her in a stress free place. There's a little planning involved. Here's how you can set this up...
Everyone hates Mondays. So make your wife's Monday a little easier by giving her a little paradise and rest. You want to spark her libido? You want to ignite her passion? Do things like this for her (with no expectations) and she will get the re-charge she needs. After enough re-charges, she will be primed and her thoughts are more likely to turn to sex, which will increase her sex drive and rekindle her desire for you.
(Of course, you can also do this on any day of the week and adjust it for different work schedules - Friday is good, but more expected - I personally like to do things that are unexpected.)
Early Morning:
When you leave your wife for work or you both leave for work, give her a big hug and a nice passionate kiss (not deep - just passionate).
Mid Morning:
When you get to work call her / e-mail her and just wish her a great day and tell her you love her.
Afternoon:
In the afternoon text her / e-mail her to say you have a nice surprise for her later tonight.
On the way home:
Pick up her favorite dessert, scented bubble bath soap and some flowers (leave the flowers and bubble bath in the car - if it's too hot, sneak them in and stash them somewhere). If you don't have candles at home, get three - the kind with their own glass jar and lid are great - no smoke - you just put the lid on to put them out.
Evening:
After dinner and the kids (if any) are in bed, excuse yourself to the bedroom and draw her a bath, light some candles, set her dessert and the flowers out along with a refreshment.
Invite her back into the bathroom and just say you wanted to give her a break and her own little slice of paradise. Tell her you'll take care of any issues with the children and will clean up any messes (like the table, kitchen). Let her know this is for HER, so she should just enjoy and relax and call on you if she needs anything.
Don't expect anything. If nothing happens, at the very least, your wife will be very relaxed and very grateful. But - you never know - you may get an invitation you're not expecting.