Nutrition & Hydration
To be honest, half the reason I do this sport, is cause I love my food and drink so much! The reward for putting my body through the rigmarole of training for an event, is so I can enjoy a beer and a burger! To me, it's all about balance and moderation. Just so happens sometimes there's not always as many calories in / calories out to warrant the reward!
“Be strong because things will get better - it may be stormy now, but it never rains forever.”
Recovery
Such a crucial part of any exercise plan is the recovery - and one that people also forget about. As you get older, it takes longer to recover and you can't bounce back as you would when you were younger, so rest can be as beneficial (or arguably better) than thinking you need to do that extra run session. Core strength takes many forms too and is sport/discipline specific so factor that into your regime as well. For some people, depending on what stage you are at in your training, a 45 min core/stretch session is more valuable than getting that last ride or run in because you feel you need to. Financially, a massage once a week leading into an event gets pricey. If you can afford it, then great but spending $50 on a foam roller and learning how to use that properly, along with some specific stretches, would be just as good for your weary body.