Generally, I avoid stakes where I don't feel comfortable. Occasionally, I'll get to a $100 or $200 buy in (for me, that's high stakes!)... And generally, I just play relatively tight and then feel sick when someone three-bets my Jacks.
But realistically, you need to play more volume. Nothing takes away the anxiety more than having been in the same spot 1000 times.
But generally, make sure those stakes are within your bankroll management... I suspect they're not, if you're feeling uncomfortable.
There are lots of mindfulness exercises you can do to keep calm and rational.
Taking good notes on your opponents can help you to make better decisions which helps with anxiety.
Playing tight and from in position is helpful.
Getting your bet sizing appropriate will also help,
But generally, anxiety over stakes is related to being at the wrong stake level (ie playing outside of BRM or simply punching above your weight and winning sattie tickets. If that's the case, stop worrying about results and concentrate on making good decisions.
remember, being results oriented will make you a poorer player in the long run. Focus on making the correct plays at the correct time against the correct opponents from the correct position...and don't forget to get the correct flop, turn and river!
best of luck.
JT