the difference between perseverance and futility is the strength of the plan before hand.
If the plan is weak, then it's usually futility
If the plan is well thought out, then it's perseverance.
In the case that a plan isn't there, I look for some kind of metric. Something to tell me that I'm going in the right direction. But this is more or less a desperate measure.
For instance, If you're starting a business, The statistics of business that fail are staggering. first year, 90% fail. Of those that are still standing, 90% fail after 3 years. The common thread that are the winning bunch is the strength of their plans and how much persevereance was used to push the plan forward. Sometimes, for a whole year, you don't know if you're doing well or sinking under. This is why you have a risk assessment or exit plan in the overall business plan.
This is cool, however the exit plan is based on interest and time available. It's definitely cool for interests, hobbies and things like that. However when it becomes more serious matters (like how am I going to make ends meet this month), having a good plan and sticking to it, is perseverance. That same act without a plan is futility: if you succeed, that's luck.For me, perseverance becomes futile when I have more important things to do with the time I an spending on it/
The one thing you want to avoid is stagnation, ambivalence, or anything that is not giving you a clear sign which way you're going. Sometimes you can't help it and this is where being creative comes in handy mixed with perseverance to get back on track.
hope this helps.