This is the heart of St Therese of Liseux's Little Way. One reason this great saint and Doctor of the Church is so popular is because her Little Way gives hope to those of us who may sometimes feel that we have to do grandiose deeds in order to please God and gain eternal salvation. St Therese explains that it is not the deed that needs to be great, but the love with which we do it. To Therese, everything was grace, even the daily humdrum chores of daily life.
Scripture backs this up, or perhaps our saint based her Little Way on scripture. St Paul's discourse on love in 1Corinthians 13:1~13 tells us nothing, even the greatest of gifts and deeds is anything unless we have love. St Paul again in 2Corinthians 9:7 tells us that God loves a cheerful giver. I know in my own life I do not always carry out my daily tasks with love and cheer~much grace is lost by this. St Therese is a wonderful model and reminder of how doing things with love can transform menial tasks into tasks that have great spiritual benefit not only for ourselves but others as well.
She promised to continue her Little Way from heaven sending forth a shower of roses and spending her heaven doing good on earth. Many miracles have been attributed to her intercession. You may often hear people who have prayed to her for intercession say that the favor was granted and they received a rose in some way, shape or form as a sign that the favor was granted.
St Therese also had devotion to our Blessed Mother. The death of her own mother was one of the most difficult events of her young life. She took Our Lady as her Mother from that time on. The video below is from EWTN's Saints Speak archives. In it St Therese speaks about her vision of Our Lady during an episode of illness.
I have also included links to a site with prayers to the saint as well as a reflection on St Therese from Fr. Steve Grunow who is the Assistant Director of Fr. Robert Barron's Word on Fire Ministries.