You seem like a very considerate lover, and somewhat of a perfectionist. You want to do the best for your wife. It's natural to be wanted, and when it happens simultaneously with both partners, you feed off each other, and a sweet upward spiral occurs. This is an awesome feeling. Sounds like you're used to your partner giving the initial spark. The simplest, and possibly the greatest thing to do to create that spark...is to genuinely enjoy her. If you're hung up on performance, you risk subconsciously transferring that feeling to her. On the other hand, if you are truly enjoying your intimate time with her, she will feel that you are turned on by her, and will respond in kind.
Taking the initiative, or being on top doesn't necessarily mean you are being physically dominating. A soft, lingering kiss on her neck while you're both going through your day can let her know that you are interested for something special later on.
I personally feel that the missionary position is severely under-rated. It gives you the opportunity of a lot of intimacy. Think of it as protecting her, shielding her with your body from whatever she had to deal with that day. You can still be "bullish" and strong, but in a very positive way.
If she's laying back, it's an ideal time for you to kiss her, touch her and rediscover her body. Foreplay is a wonderful thing that can help you reconnect as a couple. Sometimes, giving her a full-body massage with a relaxing-scented lotion can take your mind off of performance anxiety, while giving her a soothing treat. Take her to Bath & Body Works and see if there is a scent that she particularly likes. Once you are comfortable, you can move to more adventurous things. A game of Twister goes very well with lotion, and it can certainly spark some interesting new positions! I'm pretty sure you can machine-wash it on the delicate cycle.
Just don't slip off the bed. Caution: may cause injury.
Once again, enjoy her. Think how hot she makes you. Fantasize about her until you HAVE to have her. You don't have to drag her to the bedroom by her hair. But gently guiding her there, and laying her back while you're shaking with anticipation can definitely improve what follows.
And, come to think of it, a gentle tug under the right circumstances can be quite sexy - like when you want her lips somewhere, bury your fingers in her hair and CAREFULLY move her head. If you do this, you're not being an asshole, you're just playing with control. After all, it's about you, too, and she will most likely appreciate it if you showed her exactly where you like to be touched.
Good luck & have fun!!!
Oh, yeah, obligatory DISCLAIMER: make sure you're both healthy enough for sexual activity, don't attempt anything potentially life-threatening, and don't do it on your boss' desk.
Do not take my advice before talking to your doctor/counselor/other professional. Depending on where you live, you may be able to find free, confidential care. Most importantly, sometimes your shrink can be wrong. Get a second opinion.