When watching a replay watch only your macro! Learn some markers for instance I tell zergs they should always have 50 drones by 8:00 unless they are HEAVILY pressured. A little helion/marine/stalker pressure shouldn't stop you getting 50. Watch pro Terran and Protoss players replays to see when they have 50 probes/scvs by and make sure you are doing the same.
Reasons you won't reach these goals: Supply blocks, lack of constant worker production, random build orders.
Fix these things!
Another low league mistake is to just randomly build units early on. You need to identify all your scouting que's. e.g. watching 2nd gas + chronoboost to identify a 4 gate. If you aren't reading into things like gas timings and such then you need to start doing that! Only build the minimal amount of defence at each period so that you can maximise your economy!
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