Act of Contrition
O my God, I am sorry and beg pardon for all my sins, and detest them above all things, because they deserve Thy dreadful punishments, because they have crucified my loving Saviour, Jesus Christ, and most of all because they offend Thine infinite goodness; and I firmly resolve by the help of Thy grace never to offend Thee again and carefully to avoid the occasions of sin.
from A Simple Prayer Book
In our current circumstances, as getting to Confession may not be possible, this prayer - which many of us have learned as children - takes us in stages towards real love-contrition (sometimes called 'perfect contrition').
We can recite it slowly, dwelling on each phrase, while calling to mind our sins.
One of the most important challenges for Catholics in lockdown is not being able to go to Confession. As this article explains, it is also an important opportunity.
Plenary indulgences can be obtained in many ways for the duration of the coronavirus epidemic. Along with a simple explanation, here is the text of the decree of the Apostolic Penitentiary, which explains it in detail.