God made two promises to Abraham. The first, that his descendants would out number the stars in the sky. The second, that he would be given the land of the Canaanites to possess. Abraham and Sarah wanted a son so badly they could almost taste it. So when God promised them that they would get a son, they took things into their own hands to see how they could “help“ God achieve this goal. Their attempt to aid God led to problems in their marriage, problems in their household, and strife between the descendants of Ishmael and the descendants of Isaac. No such attempt was made to prematurely take the land of Canaan by Abraham and Sarah.
If we believe God is leading us into something that we already want, the temptation is significant to try and “make it happen”, but this is more likely to mess things up than bring them into fruition. If we want to see God work, we should let God work. We don’t step in and say “thanks God, I’ll take it from here”. In 1 Corinthians 4:7 Paul says, “What do you have that you did not receive?”, he recognizes that every good and perfect gift comes from the Father (James 1:7, paraphrased).
Don’t do God’s job. You’ll be bad at it.