Looking on feedback on how do people generally trim down their portfolio?

So like many folks here and other places lately, the massive run has in the market has created phenomenal run. I do want to sell some portion of portfolio and have cash on the side - I am okay to miss out on future gains.

One basic strategy is to sell the initial capital and leave free money to float. I don't have that many position that returned 100%

I'm eye balling my portfolio and returns thus far has been high 30%.

What is optimum strategy to sell? Sell 30% or 50% of the position and place it elsewhere or leave money invested and let the funds weather the storm.