I think you're right.

The first big step in Emotional Intelligence is being able to understand and regulate your own emotions, and it's the first step for a reason.

Kids who passed the famous marshmallow test (were able to resist the impulse to eat the marshmallow when unsupervised) were far more successful in later life

I have two brothers who occasionally get very angry, cut off relationships on whims and sabotage themselves through acts of defiance and misplaced protest, and neither of them is very 'successful' (however you define it). There is definitely a link.