Sounds like bad nerves, I get em too. A few things that helped me:

Exercise, especially after a "bad loss"

Take notes on all losses, you don't have to look at them, just take notes.

Make yourself a timeline: Say at 5:00 min I want to look at ramp with ling and have roach warren on way. Then at 6:00 poke ling, make sure OL is ready for sac. 7:00 poke ling, Sac OL. Over time, it will become second nature. This timing stuff can also be a negative, if say, you forgot your OL sac at 7:00 and now are freaking out about just saccing an OL.

But the best answer, is just to play more. You will grow out of your nerves, untill you start playing tourneys