How to get over flight anxiety

I am going on a 15 hour flight to Europe at the end of may! It’s my first time out of the country and I am really scared of flying! I have flown before but it was many years ago. The longest flight I have been on was 10 hours and it was almost 11 years ago! How can I get this fear of the worst out of my head so I can relax and enjoy my trip? My boyfriend is going with me as well so that helps but I am having such anxiety about it! Help! 🙈🙈