As the title suggests, I generated my own mnenomic phrase for my hardware wallet. I'm a cryptography noob and I keep seeing cryptography experts advising not to generate own mnenomic phrase. I used three different sources of pseudorandomness to generate 256 bits: throwing a dice, taking system times from my computer and using the last number to determine wether next bit is one or zero, and picking cards from shuffled deck. I did this 256 times using each method roughly 33%. I used those bits to generate mnenomic using Ian Colemans mnenomic phrase tool on airtight machine.

Does my method seem safe enough or should I follow advice from cryptography experts and use dedicated tool for mnenomic instead?