Down in the doldrums

It is amazing how the human heart can go from one thing to the next. I can be high or low. On Monday after devotions, I was high, today after reading a certain email I am low, so what is it that I trust in. Do I look at circumstances, or do I trust in the lord. I am praying for someones salvation and also for the biggest personal thing I have ever asked the lord for all my life and I need guidance, wisdom and I have asked God for whatever he is going to do, to do if quickly as I need it. I have no idea how my prayers will be answered.