Is there some way of knowing how far we have succeeded in our Spiritual Journey?

It is not easy to judge, only God and our Guru can truly know how much we have advanced. However, a simple parameter, which can give us some idea, is to see how much our mind has gotten detached from the world and the extent to which it has gotten attached to God. This is a simple rule of thumb to measure our advancement.

Do a reading of yourself. When you suffer reversals in the world, how upset do you become? If you find that earlier, you would keep brooding when someone insulted you, but now you are able to forget it in an hour's time, then you can conclude that you are progressing; your mind is becoming detached from the world, and your spiritual power is increasing; hence, you are able to remain normal in any circumstances.

Again, analyze how much does your mind yearn for a spiritual association. If earlier, whenever you had free time, you wished to spend it in seeing movies, but now you seek opportunities to sing devotional kirtans, it is a sure sign that you are progressing and that your mind is getting attached to the spiritual realm.

How to get peace of mind when someone has wronged us to no end?

This material world is like the prison house of God; souls who have turned their backs towards him have been put here.  So, we cannot expect the people of this world to behave like Saints. There will always be persons who will come to cheat us, and on some occasions, they may even succeed.  That is life; we all get cheated once in a while.  But the important thing is to learn to take it in our stride.  That is where the quality of forgiveness comes in.

If we continue to harbor resentment towards those who have wronged us, we will be unable to progress spiritually. Resentment acts like a poison on the mind, filling it with bitterness. And we keep reliving the sour experience within, pinned down to the past. Someone aptly said: "Resentment is like taking poison and waiting for the other person to die."     

On the spiritual path, we must be careful not to nurture ill feelings towards anyone, realizing that they will harm us more than anyone else.  Jagadguru Shree Kripaluji Maharaj says:

भूलिहुँ दुर्भावना कहुँ, हो न सपनेहुँ प्यारे।  (साधना करू प्यारे )

"Even in your dreams, do not make the mistake of harboring ill-will towards anyone."   

Forgiveness is a sublime personality trait that immediately releases all bitterness from the mind. It is a favor we do, not to the other person, but to ourselves. The lives of saintly people are full of inspiring stories of how they forgave their wrongdoers, and even succeeded in winning them over by their love.  

A person made an attempt on the life of Mahatma Gandhi, while he was living in South Africa. Mahatma Gandhi refused to hate the man. He said, "I shall love him, and win his love." One year later, that same man came and apologized to before Mahatma Gandhi, and wept for forgiveness. This is the characteristic of great personalities; they refuse to allow their minds to dwell on hatred towards anyone.