Matthew 10:19 - But when they deliver you up, don't be anxious how or what you will say, for it will be given you in that hour what you will say.
Jesus said: 'don't worry about how to respond or what to say. God will give you the right words at the right time. For it is not you who will be speaking; it will be the Spirit of your Father speaking through you' (Matthew 10:19-20 - But when they deliver you up, don't be anxious how or what you will say, for it will be given you in that hour what you will say. 20For it is not you who speak, but the Spirit of your Father who speaks in you. ).
Does that mean we should not prepare ourselves? No, it just means we should stop trying to figure out in advance everything we need to say and do in every situation we face. You'll wear yourself out trying to prepare for every circumstance you're likely to run into in the future. Jesus told His disciples to entrust their lives fully to God and depend on His indwelling Holy Spirit to guide, protect and equip them when the situation arose. The same goes for us.
For example, when we have to make hard decisions or solve complicated problems or confront difficult people, God's Spirit will decide the proper time and the best approach. He will also give us the right words to say. Until then, we don't need to bother ourselves with it.
If we will listen to what the Lord is telling us here in this passage, not only will we have more peace, but we will also enjoy more success. When we do have to speak, what comes out of our mouths will be spiritual wisdom from God and not something we have come up with out of our own carnal mind.
Your responsibility is not to know the future; it's to trust in God who holds the future, and be confident that you're safe in His hands.