How badly do you want to get better?
I don't ask what you're willing to sacrifice. If you're serious about this sport, it's clear already that you're willing to put your social life on the line; you have no problem spending copious amounts of time on a sport; and dropping hundreds (maybe thousands) of dollars on gear, racing, and travel is nothing new to you.
But let's say, for example, that running is your limiter. You can put in a decent swim, create a big lead on the bike, but then get re-passed by 50% of your competitors on the run. You're a strong athlete. You may not be "a runner," but you know you're strong. So you figure you should at least have a 45-minute 10k hidden deep inside you.
Here's the problem: In order to access that speed, you might have to focus just on running.
In my foray into cycling this year, I fully grasped something I should have known already: I cannot realize my potential in the individual sports of swimming, cycling, and running simultaneously. Neither can you. That's why pro triathletes don't win big-name marathons; it's why pro cyclists never win Kona.
Now in amateur triathlon, I have an awesome bike leg. That's where I do the most damage; that's where I gain my edge. But my 20-21 MPH speeds will not cut it for me in road races, criteriums, or even time trials. Part of this is a mental block (at least for me). When you've trained yourself always to save a little bit on the bike, it's tough to lay it all out in a bike race. Subconsciously, your body doesn't want to go 110% in a bike race, because it figures it's going to have to run after. I got to where I started asking myself, "Would I be able to run after this?" And if the answer was yes, it was time to get the lead out.
But most of the issue was with training. Even at the top of my game, I'm not going to be as strong cycling as a triathlete against dedicated cyclists as I would if I were only biking. In other words, I have untapped potential.
That doesn't mean that you never win a 5k or a time trial when you're training for triathlon, of course. I've gotten a few medals at local runs this year, and I've won some prize money in the bike scene. The problem isn't that I'm not competitive with runners/cyclists; the problem is that I'm not achieving my potential.
That's important, too, because there are triathletes out there who come from a background of competitive, dedicated running and cycling, and they're much closer to their potential in those sports--even when training for tris!--than I am. And if I want to beat them, I'm going to have to access some more of my own potential.
Which brings us back to the original question: how badly do you want to get better?
It's apparent to me, at this moment, that I will eventually want (or need) to put in a long-term, dedicated running focus. That means more than just a month or two in the offseason (like I did this year, after my ankle healed enough); that means like a season. And during that time, my swimming and cycling will go by the wayside. It's not that I'll never swim, or never ride. And it's not that I'll lose all the fitness and speed I've developed in those disciplines. But they won't be my focus, and I probably won't see the kind of improvement in those sports that I've become accustomed to. I'll still be able to race tris, too, although I may not have the cycling and swimming legs to be placing top 10 like I have been.
Can you tell I'm trying to talk myself into this?