Yoga Sutras 2.16
Patanjali, explained by Swami Vivekananda
हेयं दुःखमनागतम् ॥
heyaṃ duḥkhamanāgatam
The misery which is not yet come is to be avoided.
In plain words: Suffering that has not come yet can be prevented. We cannot change the past, and we must live through what is happening now. But we can stop future pain before it starts, so that is where our effort should go.
Swami Vivekananda explains
Some Karma we have worked out already, some we are working out now in the present, and some are waiting to bear fruit in the future. The first kind is past and gone. The second we will have to work out, and it is only that which is waiting to bear fruit in the future that we can conquer and control, towards which end all our forces should be directed. This is what Patanjali means when he says that Samskaras are to be controlled by resolving them into their causal state.