Imagine you're watching a stream. And say a duck or a stick catches your attention as it floats past. Normally you might follow the stick or duck as it goes down the stream, moving your eyes and turning your head and watching it until you can't see it any more. Now you're not watching the stream anymore, you're watching the stick or the duck. Every day we do this with our thoughts. What if you just watched the stream? Something floats past and you notice it as part of the stream but you don't dwell on it, it floats out of view and you don't try to hold on to it. Even if the thing that floated by was a big ugly piece of trash you don't get upset that it interrupted your view of the stream, you accept it as just another part of the stream.
That's what meditation can be like. You just let your thoughts stream by. You don't worry about them, don't analyze them, don't try to remember them, don't try to hold on to them, don't try to follow them. Just let them be had. Some days you'll have a flood of them during meditation, things you have to do will pop up, things you're worried about will pop up, random discomforts you're feeling, itches you want to scratch. Other days your mind will be more quiet, more passive. Neither of these days is better or worse than the other, they are simply different states of the stream. And if you happen to give in to grasping some of your thoughts, maybe you break your pose and scratch that itch, or maybe you start to actually think about making plans for that thing on your todo list, notice that you've done that and forgive yourself for it, to dwell on guilt about grasping a thought takes you further out of your meditation than grasping the thought did!