As a newbie trader, I discover new things on my learning adventure. Early on I realized that not all platform allow 4 am to 8 pm EST trading and, in fact, very few do even if they aggressively promote 24h trading (yes, you TDAmeritrade) but only with a handful of companies. Recently I learned that I could choose the lots to sell when holding multiple lots of a company bought at various prices, and not just the standard FIFO. Yet again (yes, you TDAmeritrade...) your broker may not necessarily make it easy to do so. For example, it cannot be done on TOS. You need to go to your TDAmeritrade account, got to your unsettled gain/losses and select the lot to sell. I attribute at least half of my few losses to this, selling multiple lots at above the avg holding but coming short on the highest cost lot. Knowing what I now know, I can sell the profitable lots and hold the others until they too turn a profit.
Etrade is super easy to sell separate lots w/Etrade Pro (not sure about their other interface). You just right-click the lot and it populates the order form with it. FYI, I use Etrade for buying/selling, but TOS for charting