The Roman Missal, though giving us “purple” days, lists today as “Ash Wednesday” and the next three days simply as Thursday/Friday/Saturday after Ash Wednesday. Sunday is the first Sunday of Lent, and the weekdays are identified according to the Sunday they follow.
Technically speaking, we observe a prelude to forty days. Consider this: if you mess up your Lenten discipline before Sunday Mass, just consider it a practice time. Literally, a pre-season. Get up, dust yourself off (but keep the ashes), and start again.
The alternative opening prayer from MR2 says it well. We cannot expect to succeed on our own will. We beg grace.
Gracious and merciful God,
you look with love upon a sinful people
and desire only their return to you.
We beg of you the grace to live this holy season,
to persevere in prayer, fasting, and almsgiving.
By the discipline of Lent
purify our hearts of all pretension,
bring us back to you,
and make the whole Church ready
to celebrate the mysteries of Easter.
Grant this through Christ, our liberator from sin,
who lives and reigns with you in the unity of the Holy Spirit,
holy and mighty God for ever and ever.
We beg grace of God. And Christ will liberate our hearts from the place where we pretend to be someone, something we are not.