When the time for action comes, when you finally get the opportunity to serve God the way you've always wanted and dreamed, the way you have responded to past temptations will have set the pattern, created the inertia, for how you respond to temptations in this time of opportunity. If you have always given in to temptations that wasted your time, drew your focus into fantasy, and required you to hide those parts of your life from what you share with God, then when you finally have the chance to pour yourself into the work you're called to do, you will carry the inertia of those distractions, those time-wasters, those sins, into the opportunity. And instead of pouring a purified, intensely focused and trained self into the work, you will pour your polluted, distracted self into the work. Your contribution to the work will be less than it might have been; the work will, very likely, be less than it might have been.
Today is practice for tomorrow. What you do in the small trains you for what you do in the large.