It's helpful to have someone act as a sounding board for your ideas and opinions but it's not essential for living a meaningful and fulfilling life.
So, yes it's important; but it's not absolutely necessary.
Is it better to, “... leave your own problems to your own mind?”. Not necessarily. It depends on what those 'problems' are. If those problematic thoughts are of a violent nature (ie. suicidal or murderous) then you need to speak to someone about them urgently.
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