Soldiers out in the field are under a constant of barrage stress. In order to complete the task at hand the military teaches them to "compartmentalize" problems into tasks in order gain success. By compartmentalizing, big things are made smaller by chunking them down into palatable bite size pieces. Some characterize this compartmentalization as F.O.C.U.S. Follow one course until success then one moves on to the next task.
In Aikido, the techniques have a lot of moving parts and it is easy to become overwhelmed. Each technique is broken down in to steps and each technique, no matter the teacher, has the same hallmark steps - ikkyo is ikkyo but just has some different nuances. In order to make the techniques "work" students should do every step and give each step the necessary focus.
How much emphasis and time is required of each step changes as a result of one becoming more experienced and/or skillful. It may appear that an expert skips steps, but noting could be farther from the truth. An expert still gives each step its due, but sometimes just more quickly.
An often miss quoted Benjamin Franklin quote is, " Take care of the pennies and the dollars will take care of themselves" is apropos to getting good at Aikido. To get good at Aikido, or anything else for that matter, one just needs to F.O.C.U.S on each step.