Not so good—Just stay busy and you'll be okay.
不要说：让自己忙起来，你马上就好起来了。

This is dismissive of the person's feelings, no matter how good the intention. It is okay to say what worked for you when you experienced grief, but make sure it's not in the form of a command.
这是对别人感受的一种无视，无论你初衷有多好，当别人悲伤时说这些的确有点用，但记住不要用命令的口吻。

Better—When I was grieving, staying busy was helpful for me, but that may or may not be what works best for you.
不如说：当我难过的时候，让自己忙起来是个好办法，但是我不知道对你是否适用。