Life lessons as #IShouldHaveKnown-That dominates Twitter

Tweeps took a long hard look at their lives, the decisions they have and haven't made and lessons they have learnt as they shared what they wish they knew when they were younger and didn't know any better. 

From romantic relationships to family relations and money, these are the responses they had to the hash tag #IshouldHaveKnownThat. While some are hilarious, others are just plain sad.