According to Osho, no—cultivating resolve is not necessary. Surrender is enough. Honor your inborn nature: if your heart is feminine—feeling, receptive—follow surrender; if masculine—resolute, organizing—follow that. Do not impose change or manufacture willpower. Begin where you are; as you are, you are accepted. Both surrender and resolve are valid paths leading straight to the Divine.
Don’t force willpower—be as you are; if surrender fits you, trust it, and if resolve is natural, use that—both reach the Divine.