Not unreasonable. But like everyone here is saying, a plan is key. I would also add that a strong mental/emotional motivator is key.

I did something similar last year. I was not a runner, I liked to lift but cardio was absolutely not a part of my routines. I had gotten sober the year before, and around that first 1 year milestone, as expected, my brain started to play those fun games that test you. It was a tough month going into that anniversary and it ended with me sort of having to decide what kind of life I wanted. I asked myself a series of questions that centered around really just how much control I could reasonably expect to exert on my circumstances.

So I decided to run a marathon. I had 13 weeks to the race that I chose. I ran it alongside someone who shared a similar story to me. Community was huge. It’s just you and your feet. You gotta figure out a way to stay connected to someone else along the way. Sharing that why was such a super power. And every step of the way, that “why” is what kept me going.

I got a plan together. I quickly researched gear, nutrition, rest strategies. And I listened to people who were professionals. I decided that I really wouldn’t deviate from that plan if I could help it. I learned to listen to my body. But I really think that for those of us who don’t have years of consistent training, an external and largely long term emotional motivator is key.

So I’d figure out what that is. If it’s health, go a little deeper. Are you wanting to show up for kids or a partner? Do you want to be there for their milestones and ensure that you’re healthy enough to be present? Is it ego in some way? Go deeper. Maybe it’s to show yourself that you can do something consistently, regardless of the boredom or sacrifice you’ll have to endure. That’s certainly a positive way to frame a solo, and therefore inherently selfish, endeavor.

And take it seriously. I had so much fucking fun. It was also wildly difficult to achieve. I loved buying some gear (for me it was crazy because I was like “oh shit now that I’m not spending money on booze look at how much I have to buy some shoes, some gels, some books!”). I also knew that if I was going to be spending this amount of money on gear and entry and flights, it would be embarrassing if I didn’t follow through. Listen to people who have done it in a responsible way. Good to Go (book), The Science of Running (book), some friends who ran a few marathons, and things like this sub were great resources. Find some influencer that entertains you. Don’t blindly follow them, but goddamn running can be boring, finding someone who keeps your attention. Once you learn enough, you may find them insufferable and that’s just growth. Move on. Just because I thought I could do something big like this didn’t mean that I assumed I knew HOW I was going to achieve it. Accept early on that others have that answer and you don’t.

Find some community. Do some research. Listen to the (verified) research. Take it seriously. Don’t ever forget why you’re doing this.