Success is to be measured not so much by the position that one has reached in life as by the obstacles which he has overcome.

This quote means that being successful is not necessarily about achieving high levels in life, such as getting a good job or becoming wealthy. Instead, it means that a person is successful when they have overcome difficult obstacles and persisted even when the odds were against them. Success is more about how a person has battled and endured challenges in order to reach their goals, rather than the end position.