Does stress when TTC stop you conceiving ?

Heard off lots of friends family and even woman in this group , when TTC it doesn’t seem to happen , all the stress , negative tests , timing sex etc , tracking bbt etc it doesn’t happen or takes so long to happen because we are stressed .... but then when your least expecting it and stopped ovulation tracking etc they got ther bfp when they had gave up hope and stopped trying . Just wondering theories on this ?? Or has it happened to anyone on this group . Feel like after 2 years of ttc it’s never going to happen 👎 opinions please ???