If abortion can be forgiven, why not do it and just ask for forgiveness after?
This question highlights a key distinction in how many people think about sin and forgiveness.
Although God's grace is sufficient to forgive any sin His people commit or have committed Scripture repeatedly warns us to never presume upon that grace (Romans 6:1-2). We should not sin with the expectation of forgiveness (Romans 3:8). If you find yourself thinking that way, it is a sign you have not yet bowed your knee to Christ as Lord; you likely do not have eternal life abiding in you (1 John 2:3-4)!
In fact, Scripture warns that presumption and arrogance amount to idolatry (1 Samuel 15:22-23). When you assume God will forgive a sin you knowingly engage in, you are believing in a false god who cannot save you (Exodus 20:3; Galatians 6:7-8). The Bible commands us to flee sinful passions and trust that what God has said is true: righteous choices are always what is best for ourselves and others (Titus 2:11-12; Psalm 19:7-11).