We're all guilty of it on occasion (or perhaps more than that) -- being our own harshest critic and at times, worst enemy. Sure, self-reflection can push you to greater heights of achievement, but not when you're paralyzed by insecurity and self-doubt. But when you teach yourself to properly channel all of that energy for good? Well, then you might just surprise yourself with where you're able to go.
1) Focus on the... bad? - Yes, we know. You're constantly being told to focus on the good around you, but in some cases, focusing on the very "flaw" that's keeping you up at night can be a good thing when done the right way. The trick is to take that focus and make it positive. Take that one trait, or seeming imperfection that's keeping you up at night, and every day take the time to acknowledge something good about it. You might have to do this every day for a LONG TIME, but stick with it, it works.
2) Turn it around on yourself - We all know the Golden Rule; treat others as you in turn, would like to be treated. Well, flip that on it's head and see where you land. Think of what you're saying to yourself internally. Would you say that to someone else? Probably not. It would be too mean! Be kind to yourself and don't hold yourself to some standard that's outside the realm of reality.
3) Reject something -- just not yourself - Too often we find ourselves spending undue energy on things we can't actually change. This can really be a downer when it comes to harping on our own body image in particular. So the next time you're going down that rabbit hole, stop. And consider whether it's the ideal that you should be rejecting instead.
4) Dilute it away - Just being realistic here, but the likelihood of being all positive all the time is, well, slim. But for every negative thought you have about yourself dilute it down with a few of the things that you dig about yourself and in the end, good WILL prevail!