This idiom is a term from mechanical engineering and specifically referring to the importance of lining up air ducts if one expects the air conditioning and heating system to function properly.
This is an alternative version and explanation for the idiom Get your ducks in a row.
1. Don't use to much of something. Example:"Go easy on the ice, I just want a little bit in my drinks." (also "easy ice") or "Go easy on the gas--slow down!" (or "easy on the gas") 2. Don't demand too much, or be to critical, rough or hard on something or someone. Examples: "Go easy on her, she's had a hard day." or "Go easy on that car door--don't slam it!" or "The coach is going too easy on the team since that last big loss."
If you go off half-cocked, you take a rash action without being prepared for the consequences. It refers to an old fashioned single action revolver, which had a half-cock position in the action where it would supposedly not fire. If you made a mistake and it was at full cock, you would fire prematurely, possibly with devastating results.