Each of these forms is correctly considered a principal part of the verb to burn: burn, burned or burnt (past tense), burned or burnt (past participle). Don't worry about which form to use; use the one you prefer. However, it would be well to avoid both when you mean "disillusioned" or "cheated"; also,"to burn oneself out" is an exceptionally trite phrase, as is "burned up" ("angry").
Dictionary of problem words and expressions. Harry Shaw. 1975.