I've long been interested in the notion of satispassio (satispassion; we could also translate it, and I think it would sometimes be more intuitive to translate it, as satispatience). It is an idea that is remarkably difficult to find a good explanation for, although there is also good reason to take it seriously.
Satispassion is contrasted with satisfaction. Satisfaction in this sense is, as Aquinas says, "medicine curing past sins and preserving from future sins". It compensates for lapses and uproots the causes of wrongdoing. The debt is paid, the balance restored. And it is very much a doing; that's in the name itself, doing-enough. By it we deliberately take on a penalty for common good. The most eminent example of this is martyrdom.
Purgatory is also a medicine curing past sins and preserving from future sins; it also compensates for lapses and uproots the causes of wrongdoing; the debt is paid, the balance restored. So it seems natural to talk about it in terms of satisfaction. But in the strict sense, it has always been the doctrine of the Church that the patient souls of Purgatory engage in no satisfaction. And the issue is that what is done in purgatory is not really something done by the soul that undergoes it. It is not a doing; it is an undergoing. Hence the name: enduring-enough. They endure the penalty of waiting until the waiting is enough.
I think this is a little difficult for us to grasp, particularly when it is combined with a crucial additional point, which is that souls in Purgatory are in a higher spiritual state than souls on earth generally are. Church Patient is a higher manifestation of the Church than Church Militant. And this is linked to another difficulty with which people often have difficulty, namely, that we can merit divine reward but the souls in purgatory cannot because they are better than we are. I don't think most people actually manage to reconcile with this; when Catholics talk about souls in Purgatory, they constantly talk as if souls in purgatory were poor cousins in dire need of our intercession and largesse. But by the nature of the case, this is backwards. Unlike us, they have absolute guarantee of Heaven. They are not worse off than we are; they are infinitely better off. They have a wealth in store for which we can only hope. They don't need our help. Praying for them is the sort of thing that could very well be seen as a bit of presumption on our part, except that we are allowed it. We are allowed to help them by prayer as a privilege graciously granted to us.
I think a possible way forward in understanding this is by recognizing that the contrast with satisfaction, although right, is also potentially misleading. It makes it sound as if there were satisfaction and then satispassion, and the two were simply separate things never coming together. But this is not, I think right. We too have satispassion; it's just that for us, we can only have it by its being a subordinate part of satisfaction. In a sense this is what is going on when we 'give it up to God'; one of the general grants of (partial) indulgence is for those who, carrying out their duties and enduring the hardships of life, raise their minds in trusting prayer to God with a pious invocation. This is effectively taking the enduring of difficulty and, as part of satisfaction, making it an act of prayer to God. That is satispassion, and is the sort of thing attributed to the souls in purgatory. But there is a key difference here. The souls in Purgatory are already united to Christ's passion in an intimate way; the attitude of humble trust in the enduring of penalty as part of this union with Christ's Passion is what they do by being souls in Purgatory. Their enduring is already itself trusting prayer to God, a penitential exercise for the purpose of becoming more closely united to Him. We, on the other hand, wavering and faulty, have to make our enduring an act of union with Christ's Passion. Our patience becomes satispatience only in the context of our satisfaction. Theirs is guaranteed. We must deliberately act in order to endure in a way that makes us one with Christ; but the patient souls in Purgatory simply endure and are one with Him.
Ultimately, satispassion, like satisfaction, is rooted in Christ's Passion; for the purposes of Heaven, a satispassion not so rooted, like a satisfaction not so rooted, is not relevant. The Cross is the only bridge to Heaven. But satispassion is the higher part, not the lower; it is like the prayer of quiet compared to verbal prayer, like the mature soul enduring aridity to the beginner in an ebullience of consolations. It is something toward which we must reach. But the patient souls of Purgatory are satispatient; they need not reach, but simply wait, being one with Christ who suffered for our sins. And as no one receives Heaven without learning how to receive, so no one reaches Heaven save by being one with Christ on the Cross, enduring until the enduring is enough.
This is all approximation and extrapolation. It is something about which we know little enough that it is almost impudent to babble on about it as I have. But I am put in mind of it by current events. As Lent draws to its close and Good Friday draws near, a great many Catholics are in a desert of sacraments, perhaps locked inside their houses due to conditions whose end is as yet unknown. That is patience of a sort. On its own it is not a medicine curing past sins nor preserving from future sins. But we may make it so by prayer and penitence. When we do, we are in our crude way approximating a higher state. And in that crude approximation we may know a little better the life of Purgatory.