Anyone who watches Doctor Who will tell you that the process of breaking in a new incarnation of the Doctor after his latest regeneration is a complicated process. I've never really noticed it that much until recently; my mother stopped wanting to watch Doctor Who because "I don't like the new Doctor." I believe that part of this is because she hasn't had as much time to watch the new episodes, so she hasn't been able to go through the emotional rollercoaster that is breaking in a new Doctor. Since I thought it would make an interesting topic, I decided to break down the various phases of adjusting to a new Doctor. So if you're new to the show, this will help you prepare for the inevitable regeneration, and if you're already a fan, some of this will probably be vaguely familiar.
*Please note: I haven't seen too many of the older episodes of Doctor Who, most of this is based on the newer seasons from when the show rebooted.*
Stage One: The Announcement
The very first stage of Doctor-Loss begins when the current actor playing the Doctor decides to quit. When this happens, there's always a feeling a shock followed by apprehension. At first you ask yourself, "How can they be quitting? They're doing such a good job!" but then you realize maybe they want to move on and, depending on your own emotional speed, you accept this relatively quickly. After you accept that the current actor is leaving, you start to worry about who is going to be picked to take his place. Usually at first there's wild speculation (i.e., it's going to be a woman/a really really high-profile movie star is taking the role/things like that) but eventually they settle on a choice and stage two begins.
Stage Two: Research
Once the identity of the actor who's set to play the Doctor is revealed, a Whovian will have to do at least some cursory research into the previous works of said actor. This can sometime lead to feeling reasonably comfortable with the new actor, but most of the time it's an opportunity to nit-pick as to why this actor is not fit to play the Doctor (they're too serious/they're not fun enough/they look funny). Typically during my research period, I look at what the different roles an actor has played and try to guess which way they're going to go with their incarnation of the Doctor. All in all, the research phase is a mixed bag as to whether it makes you feel better about the new actor.
Stage Three: Regeneration
This next stage is one of the most emotional because...it's the literal end of your current Doctor, a.k.a. the regeneration episode. I don't care who you are, regeneration episodes, at least the ones I've seen, are sad. A character you've gotten attached to is going away and some unknown is just getting plopped in their place. I'm not ashamed to admit I've gotten a bit teary watching a couple (David Tennant and Matt Smith's were pretty sad, but I personally think they were beautifully done). Anyway, so you've just gone through emotional turmoil basically watching a beloved character die and then...BAM!...there's some new dude up there acting all chipper and going, "Well howdy there! I'm the Doctor," - of course you're not going to like this new person. So now, before the new Doctor has even had a single episode, you hate him.
Stage Four: Early Episodes
Even if after the trauma of regeneration, you're not part of the I-Hate-This-New-Doctor fan club, you at the very least decide that you'll never ever get used to a new one, and it's with this mindset that you move on to the first couple episodes that feature this new Doctor. The first episodes are obviously meant to give you a feel for this new Doctor and establish the various ways this doctor is different, but also highlight how, at a base level, he is still the same. It's usually around the fourth or fifth episode that you inevitably start to accept this Doctor as your own. It can take some time to really adjust; I don't usually start to recognize the new Doctor as The Doctor until at least episode three, but it probably varies slightly from person to person.
Stage Five: Acceptance
At this point, you've once again realized, part of being a fan of Doctor Who is the ability to accept the change that comes with having a main character who changes their face (and alters their personality a bit) every now and then. Personally, I like all the incarnations of the Doctor that I've seen: not just the newer versions, but some of the early Doctors, like the Fourth Doctor (Tom Baker) and the Third Doctor (Jon Pertwee). I still go through the stages of Doctor-Loss and think, "I'll never like the new Doctor," but in time, the new Doctor grows on me and they aren't "the new Doctor" anymore; they're just the Doctor. I think sometimes people have a hard time thinking of the Doctor not as a specific person with various quirks, but as an idea. The Doctor may have different faces, quirks and companions, but his basic moral code and sense of adventure never change. Inevitably, you get attached to the current Doctor, because he still is the Doctor, and everything is great...until the cycle begins again, when the actor playing the Doctor you've come to love announces they're stepping down.