In the car assembly line, the maximum rate of production is = the lowest common rate of all components production. ONLY the lowest common rate of production.
Hence, the input car part that is the slowest (most lagging) is the one in control of the production rate. Only a change here, will impact the output.
In chemistry, there exists a similar concept: Rate Determining Step.
See progress in terms of speed. Find the critical constraint that is reducing the rate of progress.
Only solve that, until it isn't the critical constraint anymore. Then move to the new critical constraint.
Any neuron spent on anything else is motion, not progress.
A string of critical problems solved, leading to the outcome is the critical path. This is the holy grail of productivity.