Thanks all!
At this moment, I'll do nothing (just leave the funds in my account). Knowing that I got my initial investment out gives me peace of mind.
I'll see what the Bitcoin price is doing, and then decide whether I want to "dollar cost average" 50% of my investment again, or want to use it in another way.
If you are not comfortable that your initial investment is on BTC. Try to invest your USDT on passive interest like staking on Binance. In that why, Your money will still earn even though it is just sitting to your wallet while the other half is on cryptocurrency with volatile price.
Base on what you mention. You are a passive trader type so definitely you must not keeping pressuring yourself on investing in cryptocurrency in the long run.