God the Father had the plan of salvation worked out before He even created the world. Most of us would not have created the world and man if we knew the heartache and terrible sacrifice it would cost. But God is not man. In His judgment (which is the correct judgment) the prize was worth the cost.
We were chosen in Christ before the world began. The Lord did not choose us by our merit, but solely by our acceptance of Christ which His foreknowledge allowed Him to do before the foundation of the world. In the strictest sense, we were not personally chosen, but Christ was chosen and all those who are ‘in Christ’ partake of His being chosen by His Father. Just as we are the beneficiaries of the covenant between God the Father and His Son Jesus, so we are chosen because we chose God’s chosen, i.e. Christ. The Father would no more reject us than He would reject Jesus because we are accepted by the Father through Christ.
None of us can claim that we are without blame in the sight of men because man looks on the outward appearance (1 Sam. 16:7) and all of us have sinned (Rom. 3:23). But the Lord looks on our born-again spirit which has been regenerated in Christ and He sees us holy and without blame.
If you look at any color through a red glass, that color becomes red. The same thing would happen if you looked through a green glass. Everything would become green. In a similar way, God looks at us through Christ and everything in our life becomes covered by the blood of Jesus. We are holy and without blame before Him because of His love expressed through His Son.