Advice on how to relax during stimulation?

I’m a very stressed person in general, and often at the beginning of sexy-stuff any stimulation down there feels like it’s about to be painful. The only times I seem to be able to relax enough from the start is when I am slightly tipsy :/ It happens both with self stimulation but more so with my partner. Really sucks to have to mentally force myself to keep going until I get close enough to where it starts feeling good. Any advice on how I can chill out?