An event in life with a negative outcome of something that happened from one’s own doing, or from a doing of another, is usually what an error is for humans.
The above is the beginning of an answer I submitted on Quora to the following question:
Is it true that there are really no errors as all errors lead to suffering which ultimately leads to enlightenment as per Eckhart Tolle?
The answer continues with...
Suffering is usually continued focus on negativity.
Enlightenment is a process of getting insights during the process of spiritual awakening.
I somewhat agree with the first sentence in another answer, in that suffering makes enlightenment possible.
I also feel from my own direct experience of spiritual awakening that suffering also makes awakening MORE possible.
Also from my experience, I feel that spiritual awakening happens when strong desires and beliefs start falling apart, and especially when your mind, and that of others, cannot fix your suffering by doing something, usually externally, about it.
Even though spiritual awakening is easy in principle to manage, it is often not simple in practical day to day life.
To summarise and from my experience, spiritual awakening and knowing how to manage awakening leads to enlightenment. Spiritual awakening is a continued process which creates enlightenment. Enlightenment is not a destination, it provides continued and highly personal insights of the person’s being and doings, and usually explains a lot of how and whys of your behavior and sufferings.
Eckhart Tolle woke up one morning feeling different. Apparently, he lost most of his thoughts and internal chatter, but it took his mind a few years and interaction with spiritual teachers to realise what had happened and what was happening to him.