The most common way we show love to someone is that we try to act in ways that please them.
Paul urged the believers to Thessalonians to keep on living holy lives, as they already were doing. The only way a believer can live different from the world is because he knows God.
Holy living must be consistent, not a mask to be worn among the believers and discarded when dealing with unbelievers.
Saving grace is always accompanied by sanctifying grace. Do not despair if you are struggling with sin, for the struggle is a sign of faith. Question if your faith is not troubled by sin at all.