The actual quote is “譬如为山，未成一篑，止，吾止也。譬如平地，虽覆一篑，进，吾往也。”
The meaning is “孔子说：“做学问好比积土成山一样，只差一筐土而没有堆成山，停止了，是我自己停止的；好比平整土地一样，即使只倒下一筐土，前进了，也是我自己前进的。” (Source: http://www.bjhrwm.gov.cn/ctwhjy/yryj/t20110805_401107.htm)
In English, it means that studying (gaining wisdom) is like piling soil to make a mountain. If one stops short of one basket of soil to make a mountain, it is a pity to stop. It is also like filling a deep hole with soil, every basket of soil you pour in is progress.