What do you mean by motivation?
Sometimes, Christians think they should only "walk with God" when they have a strong, positive desire to do so, a sort of "warm fuzzy" about doing so. But this isn't actually the basis for why a Christian should walk with God as a "living sacrifice" to Him. Paul explained that it just makes sense, given who God is, that we live as "sacrifices" to Him all the time.
Romans 11:36 - 12:1
36 For from him and through him and to him are all things. To him be glory forever. Amen.
1 I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship.
See? Paul didn't tell the believers at Rome to have a good feeling about being a living sacrifice to God, a strong, positive desire to be one; he just pointed out that it's reasonable, it's entirely sensible, to be a living sacrifice to God because "from Him, and through Him and to Him are all things." We think in this way when it comes to, say, a dentist, right? I don't ever have a "warm fuzzy" about going to his office for dental work. But it makes good sense, it's reasonable, to see him for dental work. And so, I go. In the same way, we go God's way, we live as He tells us to do, because it is the sensible, the rational, thing to do, not primarily because we really want, in the moment, to do so. If we can operate in this way with our dentist, or with being educated, or with exercise and diet, we can operate this way with God, too. And, as we do, the "warm fuzzies" for God will eventually follow.
