EAs, typically designed as a fully formed trading system, get a bad reputation for draining accounts. But there is no reason for them to be fully formed systems. There is nothing that requires that.
EAs can be designed to execute a rule once. For example, you are watching a ranging pair. Overall, it is trending upwards and you want to enter the trade on a swing low. So you can code an EA to execute once and enter the position on the stochastic being oversold and now moving upwards.
You let your brain do the hard work and figure out how you want to enter the trade and then hand off the waiting work to the EA.
An EA can also handle the backside of a trade, dealing with a complicated exit strategy. To do this effectively, you can use a Script to enter the trade. By entering the trade with a script, you can attach a Magic Number to the Order. This number will mark that trade apart from any other manually entered trades, allowing you to find it easily with your EA.
From here, you can design interesting exits like a trailing stop where the trail varies along with the volatility. Or even a 3 part exit with multiple profit takes.
Taking these ideas one step further, you can write a fully feature “Exit” EA and a series of scripts. The Exit EA performs specific exits depending on the Magic Number attached to the order. The scripts allow you to open an order with the specific type of exit you want.
The real goal is to utilize your brain as much as you can and offload the mindless waiting to a computer program.