Bhagavad Gita 8.14अनन्यचेताः सततं यो मां स्मरति नित्यशः।तस्याहं सुलभः पार्थ नित्ययुक्तस्य योगिनः ॥

I am easily attainable by that eversteadfast Yogi who constantly and daily remembers Me (for a long time), not thinking of anything else (with a single mind or onepointed mind), O Partha (Arjuna).Commentary Constantly remembering the Lord throughout the life is the most easy way of attaining Him.Ananyachetah He has no attachment for any other object. He will not think of any other object save his IshtaDevata or tutelary deity.Nityasah For a long time, i.e., till the end of life.He who remembers the Lord by fits and starts or he who remembers Him for six montsh and then leaves the practice and then again remembers Him for six months and so on cannot attain Him. (Cf.IX.22,34)