Of course it can be done,but don't preasure yourself too much about it.It has alot to do with genetics.Some people have naturally longer muscles than others.It also has a lot to do with age.If you started MA as a young child and stretched a lot while you were developing,your muscles would be longer and you would kick higher.That's one of the disadvantages that people who start MA's later in life have to deal with.I started training when I was eight,now at 41,I can still do fingertip pushups with ease only because I did a lot of them as a child.I also have the ability to kick over my head,same reason.My kids can kick as high as they want and do full splits with ease,they have a little genetic advantage over me.As adults,It's so important that we know our phisical limitations,otherwise,injuries will hold back our training much more than the younger ones.There's nothing like feeling especially good while sparring or training one night and end up getting carried away and wind up with an injury that makes you rest for six weeks and you never really get over.Instructors always push us as far as they can,but sometimes,you really need to pull them aside and tell then how it is.If you have a good instructor,they don't want to see you hurt or injure yourself further.If they don't listen,take a complete break from the action and wait until you feel you are really over it before returning to the same school or start a new one.