刚刚 means just at that moment, emphasizing the point of time
1.我刚刚起来。I just wake up (emphasizing wake up just short before)
刚好 means do something just at that moment, emphasizing the action or the event at that time
2.我刚好起来。I just wake up ( emphasizing at that time I 'wake up' not doing something else)
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加油↖(^ω^)↗