When fighting against the evil inclination, use the same strategy he uses. When he tries to prevent you from doing good deeds, tell him, ‘It’s just for this once,’ or, ‘I’m only going to start doing a little bit,’ and similar statements that will enable you to get started. This way of talking to yourself lessens the difficulty of a task.
Think of a good deed that you would want to do, but don’t do because you feel it will be difficult for you to continue doing it. Imagine that you will do it only once. Then take action.
Sources: see Rabbi Eliyahu Eliezer Dessler – Michtav MaiEliyahu, vol. 3, p.293; Rabbi Zelig Pliskin’s “Consulting the Wise”