Yeah, Mustachian first-world problem, right? I had a similar feeling a little while ago when I got a $5k/year raise, and felt kind of guilty because I know lots of people would love to see that kind of income bump, but my thought was "meh, thanks, that's nice, but it feels kind of meaningless since my net worth can easily jump up or down that much in a day".
All the previous advice was really good. I don't think there's any good way to remove the de-motivating force market fluctuations have upon expense-reduction, so the only trick I know is to draw separate motivation from other sources to counteract that de-motivation. You just have to trust your intellectual side that says "flexing my frugality muscles DOES matter!" even though the net-worth tracking is devilishly trying to tell you otherwise, and then take separate motivation from that activity (maybe easier said than done).
Also, if you've only been tracking for the last 8 months, you've only seen pretty positive market conditions, with the market gains making any savings-gains look pretty inconsequential. But in a falling market period, it might be easier to shift your focus ("aughh, I don't want to look at my net-worth!!!") and draw more inspiration from the income/expense view of things. And then maybe the "respect" you gain for that side of things will stick with you even when the market goes back up again.
In Quicken, I do regularly look at my current net worth number, and also at the history via a nice graph which filters out some of the day-to-day volatility. But then I also look at my expenses-to-date. I don't really track month-to-month expenses or target a budget, but for almost a decade my goal has been to spend less than $20k/year, so that's the number I keep an eye on. "It's July and I'm only at $7k? Awesome!"
Also, I do twice-monthly auto-investment, at a rate that attempts to keep my cash account at a constant level. If I notice my cash account steadily rising over a period of months, I'll increase the amount of the auto-investment to counteract it. The effect is to further separate frugality-flexing from investments in my mind. If I start spending too much money (or making too little), my cash account would eventually drop to 0 and I'd "go broke". Obviously I wouldn't actually be "broke", since I have gobs of money in my investment accounts, but since the idea of withdrawing from my investments (or even lowering the amount of auto-investment) seems abhorrent to me, the mind-hack seems to be effective in focusing attention on frugality.