What are the indicators of certainty?

The first Shia Imam, Ali ibn Abitaleb (AS) said: Certainty (Yaqeen) is based on four pillars.

1. Clever/intelligent insight (the capacity to gain accurate and deep understanding)
2. Wise discovering/understanding of realities
3. Take advice/take heed from the incidents of life
4. Staying on the right path of the forefathers/predecessors [1].