Actually, I've found the number one thing you can do to make yourself feel beautiful is to tell yourself you're awesome and then go out and act as if that's true. And soon, it will be. It sounds like a cliche, and yes, it's easier said than done, but confidence is beautiful. I'm not much to look at, for example, but when I forget about that, others do too. I've had people fail to recognise me in photos because I "didn't look half as good as I seemed in real life"!
That's very true. I remember in high school I thought the most popular girls were beautiful. They believed it and they looked, dressed, and acted the part. They had the confidence so everybody else thought they had it going on too. Looking back at old year book pictures, many of the quieter less trendy girls were actually more beautiful (in my opinion).
I do think I lack confidence. One negative comment about my looks drowns out 20 positive comments. My nature is to tend to let other people's opinion matter too much (especially the people who are negative and shouldn't matter). A lady trying to push make-up or a weasel at a nightclub makes a negative comment and it fills me with self-doubt for days. I hate that I let their opinions count for so much, they really aren't worth it.
Most people can't wave a magic wand and make themselves feel better. I agree with the idea other posters had. Pamper yourself in some way or do something that takes your focus off your looks entirely, like go on a bike ride, a day at the amusement part, spend time enjoying nature, volunteering, or whatever else you like to do.