We are "called to be holy." God the Father wants His children to be, act, work, think, talk, love, and live as He does. This is the meaning of holiness: to be like God "in every aspect" of our conduct (1 Pt 1:15).
Holiness is a gift from the all-holy God. Only by His grace can we become holy. Holiness comes through the Holy Spirit, that is, the Spirit Who makes us holy. However, we must choose to accept the Spirit's gift of holiness.
Without holiness, "no one can see the Lord" (Heb 12:14), that is, go to heaven. Therefore, the Lord orchestrates the events and details of our lives to give us a greater desire for holiness. He even allows us to suffer sorrows and tragedies to help us grow in holiness. In other words, He gives us some purgatory before our deaths. Moreover, holiness is so necessary that the Lord will purify after death those committed to Him and delay their entry into heaven to complete their holiness, if they are not yet "perfect in holiness" (1 Thes 5:23). However, to benefit from the Lord's organization of our lives to foster our holiness, we must trust the Lord, humbly deny ourselves, and obey Him. Then we will desire more strongly to become holy and we will become holy, be pleasing to the all-holy God, and live with Him and the holy ones forever in heaven.