With Leo, Kim and I are finding that we need to celebrate mini-milestones. If he rolls over and sits up without assistance, applaud! If he sucks his thumb (a big deal for a child with an oral aversion) be sure to kiss him and tell him what a good boy he is.
Here is a video of one of those mini-milestones, filmed just this evening:
Yup, look at that, he's strong enough to stand himself up.
Look out, world. Leo's coming!