Genesis 16:1-6 NIV
 Now Sarai, Abram’s wife, had borne him no children. But she had an Egyptian slave named Hagar;  so she said to Abram, “The Lord has kept me from having children. Go, sleep with my slave; perhaps I can build a family through her.” Abram agreed to what Sarai said.  So after Abram had been living in Canaan ten years, Sarai his wife took her Egyptian slave Hagar and gave her to her husband to be his wife.  He slept with Hagar, and she conceived. When she knew she was pregnant, she began to despise her mistress.  Then Sarai said to Abram, “You are responsible for the wrong I am suffering. I put my slave in your arms, and now that she knows she is pregnant, she despises me. May the Lord judge between you and me.”  “Your slave is in your hands,” Abram said. “Do with her whatever you think best.” Then Sarai mistreated Hagar; so she fled from her.
I am a classic Type A personality which means that I am impatient, I expect everything to have happened yesterday. I get frustrated when I have to wait in line, I get bothered when things don't go as efficiently as I planned and I am especially annoyed when something I expect to happen immediately seems to take forever.
The great temptation for people like me, is to 'make' things happen. To push things through before their time. To take matters into my own hands and manufacture the desired results.
However, when I force what God hasn't endorsed, it rarely goes well. I normally have to spend the ensuing days trying to undo the mess I've made.
God had given Abram a very definite promise of a son and heir. However, both he and Sarai got tired of waiting on God. They figured, we'll give God a hand. We can make this happen. And that's where it all starts to go incredibly wrong.
There are certain times when we should contend for God's purposes in our lives, that it is right for us to proactively move and act and push and lay hold of what God has for us. That we press through obstacles and aggressively resist hindrances. Jesus talked about this when he said:"From the days of John the Baptist until now the kingdom of heaven suffers violent assault, and violent men seize it by force [as a precious prize]." (Matt 11:12 AMP)
This 'seizing by force' might involve intense prayer and intercession, fasting, prophetic decrees and spiritual warfare.
However, there are other times, when God has given us a promise so clear and definite, that we simply need to rest in that promise and receive it by faith. This is where we simply "receive the Kingdom of God like a little child." (Mark 10: 15)"We....imitate those who through faith and patience inherit what has been promised." (Heb 6:12)
The key lies in knowing when to proactively seize and when to posture ourselves simply to receive. When to contend and when to rest.
From my experience, when God has clearly and explicitly given a personal promise to us and reiterated it again and again, we declare it to be true and simply wait with faith and patience to receive it.
However, when God's Word gives us promises that we spiritually discern are being resisted by the enemy, when it feels like all of Hell is coming against us, that's when we step up boldly and use our authority to war against opposition, stand firm against attack and take ground which is rightfully ours in Christ. We fight from victory not for victory.
Don't force what He hasn't endorsed. Don't kick doors open that God has shut. But don't sit passively doing nothing when the Father wants you to contend for His promises and defend what He has given you.