Let me be singing when the evening comes

I love to sing! Especially worship music. Now, I would say probably most people around don't enjoy hearing me sing, but I still love it! There is something about hearing a worship song and totally agreeing with the words and feeling alive in the Lord while singing it.

However, some songs I sing out of deep conviction. I want them to be true. I want to feel that way or live that way towards God.  A couple of months ago at church we sang a song called "10,000 reasons" Here are the words that are hard for me to sing:
Whatever may pass, and whatever lies before me
Let me be singing when the evening comes

Let me be singing? Sometimes that is hard. Sometimes I don't want to praise God for what He is doing. WHATEVER may pass. I mean, I am ok with praising God when good things come, but to still be singing when I am having a rough day? That is a whole lot harder. But, I do want to be singing when the evening comes. Because, whatever lies before, it is no surprise to Him. So why allow myself to be sad about something that is from His hand?