I have done loads of lateral flow tests, never had an invalid one. I'm a bit pathetic about them - they really make me gag - but I seem to be perfectly able to do them.
Did my first pcr this week, and it seems that I fucked it up as they weren't able to read it. Went for another one this afternoon and fucked up my first attempt then as well because the bloody stick made me sneeze when I stuck it up my nose, so they made me do another one. Fair enough. I then did the next one but can't be sure that I didn't touch my tongue when I was doing the tonsils bit but I was too embarrassed to ask for yet another swab so I just carried on with it. 
I'm now convinced that this is going to come back invalid as well.
Am I just incapable? I'm pretty sure that the result will be positive when I do finally get one. I'm going to be in isolation forever at this rate!