Growing up Southern Baptist, I never really was exposed to Ash Wednesday or Lent until I began attending a United Church of Christ church. Even then, it was somewhat non-traditional.
Ash Wednesday is traditionally representative of the dust from which we are formed, a reminder that someday we will return to dust. The UCC church I attended when I first began practicing Lent held an additional interpretation. In their tradition, we were given pieces of paper in order to write down our fears, insecurities, and wrongdoings of the previous year, and they were placed in a bowl. At a specified time during the service, they were then lit. These were the ashes which were then crossed on the forehead. The idea was to burn away our fears and insecurities and start a new beginning during the period of Lent.
Lent traditionally represents the 40 days Jesus Christ spent in the desert before beginning his ministry. Fish is traditionally eaten on Fridays, and Sundays "don't count" and therefore the practitioner is allowed to indulge in whatever they are fasting from.
The Advent season leading up to Christmas (although I primarily focus on Yule) and the Lenten season leading up to Easter (although I'm still personally grappling with the meaning of Easter for myself, as I acknowledge Ostara moreso and Easter is solely a social/family gathering holiday for me) are the only real Christian holdover practices at this point in my life. So what do Ash Wednesday and Lent mean to me, a Unitarian-Universalist Pagan?
I resonate well with my previous church's practice of utilizing Ash Wednesday to rid oneself of guilt and insecurities of the previous year. Most of us do so on secular New Year's Eve - or at least attempt to - but by Ash Wednesday we've fallen back to old habits and ways of thinking, as well as committed new mistakes which can lead to feelings of guilt. It's a reminder that forgiveness and letting go are continual processes and active choices from day to day, rather than something that is done once and it's over. Additionally, it's always a good idea to take a break from old habits and routines, and trying to engage in healthier ways of living. Lent provides a perfect framework for doing so - it's sandwiched between easy to remember start and end points (Ash Wednesday and Easter), works in "breaks" (Sundays) so that we can have realistic goals for ourselves and not give up at the first faltering, and allows for us to have a more spiritual mindset when doing so.
Me, I'm working on using this time to read more, write more, and find ways to study and connect with the deities whom I feel most called to. Jesus may not be one of them any more, but I'm thankful for the groundwork that the best of his followers have laid for me.