Colossians 3:23 Whatever you do, work at it with all your heart, as working for the Lord, not for human masters
When you want to make a good impression it is best to make sure that you do so with all your heart rather than trying half-heartedly. Others will see through your actions very quickly if your heart is not in your work.
When we see others say that they believe in Christ and then run off into the world and follow worldly ways we begin to ask whether they are sincere in what they say.
Others will look at us twice if we do not follow our own hearts because they will know that we are doing something just because it has to be done and not because we want it so.