Dynamic - Dynamically Loading Controls And Persistence?

I am loading a series of controls in the Page_Load event. However, I have to recreate those controls each page load, which means storing their data elsewhere. This is cumbersome.

protected void Page_Load(object sender, EventArgs e)
{
MyControl control = (MyControl)LoadControl(...);
control.Initialize(GlobalClass.controlData);
//^gives the control the data it had previously.
//Or use ViewState["controlData"] if serializable.
Controls.Add(control);
}

I feel like I should be using if (!IsPostBack) {}, but I don't know how, or why. In contrast, if I place the controls into the markup, then the controls seem to stay persistent. For example, a button in mark-up will remember any changes to its Text property (I think?).

<asp:Button ID="buttonText" runat="server"
Text="Text Segment" onclick="buttonText_Click" />

How do I maintain some sort of persistence with dynamically added controls, like controls added via mark-up? This would save me much work and frustration.

(I've coded for a small eternity, but the more I do ASP.NET, the more confused I become. Which is exactly the opposite of what how I understood learning to work :-P.)