Those are not surprising returns. First, we've had an epic rally since January. Second, I suspect you are trading stocks that have more volatility than the marketplace. Volatility is like leverage; it magnifies both gains and losses. Because the market was shooting upward, your leveraged bet shot up even more.
AAPL is up 23% YTD.
AMZN is up 18% YTD.
The S&P 500 is up 14% YTD.
So basically you captured a fraction of the market's return by being in the market a fraction of the time. Had market returns been negative, you might have captured a fraction of the losses.
Side note of interest: TD Ameritrade offers commission-free ETFs, at least one of which has a lower expense ratio than the comparable Vanguard fund. SPTM is a total market ETF comparable to VTI, except SPTM is commission-free. SPTM also has an expense ratio of 0.03% compared to VTI's 0.04%. You could buy one share at a time every single day commission-free as you save up the money if you wanted to, and shares are only about $35.68 compared to VTI at $146.73, which means you'll never be stuck with $100 in sidelined cash in your account. There is an extra fee if you sell within 30 days of buying, but that's not a problem since you are a buy-n-hold investor, right? ;)