Well to start, optimistic thinking is positively correlated with happiness. Optimistic people are happier and happy people are more optimistic. Optimistic people are also more resilient, are less affected by stress, and worry less often. All of this should make sense to you in the context of everything I have discussed. Resilience and happiness are a function of the types of thoughts we have and optimism is a way of thinking. So yeah, optimistic thinking contributes to both resilience and happiness.
