Just because it is called day trading, there is no rule that says one must trade all day, every day.
I do not have a daily goal, but my goal is to earn 500 points ES every 500 trades. If I trade the ten-year or crude (rarely) if ES seems dead, I adjust. 3 ticks ZN = 4 ticks ES = 5 cents CL
If I HAD a daily goal, I wouldn't quit just because I reached it (can't imagine Michael Jordan calling it a day because he reached his "goal" of 40 points), and I would not necessarily feel badly if I did not make the goal. You cannot tap oil from a dry well--some days are just not volatile enough to pull out some arbitrary amount of profits.
I would be reluctant to quit early unless there was a good reason (plans, time with family, time for fun, afternoon delight, etc). Even with the VIX down, the markets are more volatile than they were for years, when the S&P some days wouldn't move eight points full circle.
Who knows how long it will last?