On market sentiment and position sizing - how do you balance?

I'm still trying to get my head around how to practically apply market sentiment polls. It's one thing to see a poll that says 70% are bullish $EURUSD, but if I then size a position based purely on that, it feels like I'm chasing. Do most of you use these polls more as a contrarian indicator, or is there a way to integrate this data into your risk sizing without just following the herd?