“When the arms bend, the power ends.” A cue I learned from Mike Burgener in my weightlifting certification. This is a cue used in the first and second pull of a snatch and/or a clean.
What does this cue actually mean? When you perform a clean or a snatch, if your arms bend prior to your hip extension the weight of the bar ends up being transferred to the arms instead of the major muscle groups of the core and legs. So essentially when your arms bend you are losing a significant amount of power which in turn will limit the amount of weight you can move.
How do you fix this? Like everything else you need to practice form and technique to break this habit. It takes time and patience