To me, keeping a "stiff upper lip" isn't so much about ignoring negative emotions, but more about behaving in the right way even when emotions pull you the wrong way. In my experience, exercising that skill doesn't create emotional problems, but solves them.
Be like a rocky promontory against which the restless surf continuously pounds; it stands fast while the churning sea is lulled to sleep at its feet. I hear you say, "How unlucky that this should happen to me!" Not at all! Say instead, "How lucky I am that I am not broken by what has happened and am not afraid of what is about to happen. The same blow might have struck any one, but not many would have absorbed it without capitulation and complaint."
This stance is immoral in many ethical systems. Not to mention everyone has a breaking point.