The days of resolution setting are days of big dreams. You’re going to have a good year, a great January. You’ll finally pick up that exercise habit, or write that book, or clean your house—any of which are possible, once you decide what other thing has to give.
Everything you do takes time, mental energy, and usually money in some form. Every hour you spend at the gym is an hour you’re not writing your novel or prepping your meals or KonMari-ing your clutter. I believe in you; I believe you can do anything. But I don’t believe you can do everything.
So, before you go a step further toward your new habit or your ambitious goal, take a minute to decide what you are de-prioritising to be able to fit this new thing in. Maybe you’re going to read more books by watching less TV. Maybe you need to negotiate with your partner so they get the kids ready in the morning while you’re at the gym, but then you take over bedtime while they get a free hour for their pet project. It’s fine to get creative. You may even find you can fit in more than you thought.
It’s also fine to give something up temporarily. Maybe you take a break from the gym to make time for that decluttering. The trick is to have a plan for getting back into it. Maybe you swap out daily gym sessions for twice-a-week home workouts, and suspend your membership for just one month. Then, come February, it’s gym time again. Better to plan that out than to let it happen by accident and have no plan to recover.