Do all temptations come from the bad angels? Some temptations come from the bad angels; but other temptations come from ourselves and from the persons and things about us.
Do not love the world, or the things that are in the world. (I John 2:15)
Can we always resist temptations? We can always resist temptations, because no temptation can force us into sin, and because God will always help us if we ask Him.
And he has said to me, "My grace is sufficient for thee." (I Corinthians 12:9)
Further reading: CCC 2846-2849