Sounds like a prudent move on your part. If your position size...

Sounds like a prudent move on your part. If your position size meant the SP volitility was scary, it makes sense to reduce your weighting.

By retaining half your holding you still receive the benefit of any future upside.

Its taken me a number of years to consistently achieve portfolio weightings that I feel balance risk/reward & volitility. Life is too short to be in a position where your investments are stressing you.