I think that basing a character on yourself is never a very good idea, especially if you’re basing it on the kind of person you want to be. The person you wish you’re more like is obviously going to be a better version of yourself, and you’re going to want the best things to happen to you. Going along that line of thinking, a main character based on who you want to be would probably turn out being perfect and wonderful and adored by everyone, and nothing drastically bad would ever happen to them (and if it did the conflict would be solved very quickly). This wouldn’t make for a very good character or story, because all characters need flaws and imperfections and all stories need problems and conflicts to make them enjoyable and realistic. Of course, if you could create a character based on yourself and still avoid all the problems then you should by all means do it, just remember to be careful about it.