Elder Paisios was asked once:
`When I went to the university, abba, I could see my progress in the school grades I got. But here in the spiritual life I have no idea where I am.`
`You can control it paying attention to your thoughts. If you have bad thoughts all the time and you cast them out and they come back and you cast them out again you should know that you passed in the class of repentance and you strive. If sometimes you have negative thoughts and you also have moments with good thoughts and no bad thoughts then you can give yourself the grade. If you see for instance that the bad thoughts decreased and the good thoughts increased you should know that the zeros decreased and the 10 grades increased. When the bad thoughts stop coming and you have only good thoughts then you should know that your heart was purified and it became the Cave from Bethlehem.
(Pious Paisios the Athonite, Letters, Evanghelismos Publishing, p. 164)