THIS is the reason why I usually advise people to start with season go through it all and then go back to season 1 when they've been hooked into obsessive Whovianism.<---you call yourself a whovian! You start on season one. Never skip nine.
As a response to 10 was holding it in so he could see all his companions again as himself and could do no longer when he reached the TARDIS. The build up of energy made it explode out of him whereas with 9 he just let it happen.