You'll see the proverbial light at the end of the tunnel, and the knowing that this process is beneficial to your personal development will be energising. (a bit like sweating at the gym is for your body)
It's like walking an amazing path that has some challenging rocky patches ... those rocky patches don't mean that the path is not worth walking. They can even make it more exciting, and you learn to navigate a rocky patch, what a valuable skill!
So let's take the context of relationships. Many years ago, before my current relationship, I used to think naively that a sign of the "right" relationship was that it was always in perfect flow without having to put much work into it. I now know that precisely because it's so right it's worth putting work into.
I learned the same in my business, and you can apply this to any other area of your life (your career, business, relationship, a goal or dream you have). If it means enough, you're willing to put in the work.
By putting in the work, you grow as a person, and often your career/business/relationship/dream grows as a result. But at the very least you've got the personal growth and that is priceless!
Whilst there may be hard or scary times, when you put yourself on the line, put a lot in and don't know how it will work out, what it means is you're being brave. You're taking a risk, for the potentially big payoff. It might turn out well, or it might not. But you are living courageously and fully.
So whether something we care about is worth persevering with or not, isn't measured by just how well things are going. It's measured by how much we care about it and how much we're growing through it as a person.
When things aren't going "ideally" for you, don't be too quick to judge the endeavour as the wrong thing to pursue. Or a relationship to ditch.
Rather, assess how much you care about it, and how great it can be if you're willing to learn through it.
And then if it's really worth it for you, re-commit with all you've got. Make a firm decision, and start taking the right actions that you're guided to take.