Ambitious is etymologically related to Ambition. Ambition would make you want to Study. Study is a synonym of Work. Work is related to Effort. 
Thinking can be used for Understanding. 
Ambitious --EtymologicallyRelatedTo--> Ambition --CausesDesire--> Study <--Synonym--> Work <--RelatedTo--> Effort 
Thinking --UsedFor--> Understanding 