I saw an order get placed today that I forgot about, so tried to cancel it in my Profile. Will that cancel my order that's already been placed?

No. Cancelling/skipping/delaying/editing on or after your order date will not apply to your current order that's already been placed. Those changes will only apply to your next order. 

Our fulfillment team works extremely quickly to fulfill orders, so once an order is placed, it can't be cancelled. Any subscriptions changes made on your order date will only affect future subscription orders.

Gainful always sends an automatic reminder email three days before your next order as a head's up, to give customers the opportunity to postpone, reschedule, or edit an upcoming order.

Due to the personalized nature of Gainful products, we cannot offer refunds or returns for unwanted orders that have already processed, shipped, or delivered.

For this reason, customers can manage their subscription at anytime before their order date by logging into their Profile at gainful.com.