Yes, it's frustrating when the goalpost moves farther away.
I was lucky--I started investing in the mid-80s, and the expectation of 8% real returns made it easy to stay motivated to put money away every month. It would be harder today, but even more important.
Well, there's this "cheery thought:" When stocks eventually take the plunge from their presently high PE ratios, you'll be able to buy them more cheaply with any money you rebalance and with your continual contribution from your paycheck. And, at that cheap price level, perhaps the dividend yield will go back up to something approaching the historical average.