Everyone's done something stupid while boating, everyone! Sounds like you're getting all yours done right up front and the best I can tell, it has to get better Peke.
Rule #1 in my book is never getting in a hurry and taking plenty of time, this includes before you even back your boat into the water. Make a checklist and go by that before start; batteries fully charged, drain-plug inserted and tight, life jackets, flare, whistle, horn, etc.... etc.... plenty of fuel and a reserve or back-up can of fuel.
Start your engine after you've backed into the water and let it warm up before taking it loose from the trailer. Never, never start your engine out of the water. The little impeller that pumps cooling water up to the base of your engine block depends on water to keep it lubricated. Made from material similar to a pencil eraser and it will wear out if you "dry" start it and run while out of the water.
And after you've done everything to make sure you're safe, and the boat\motor are "sea-worthy" just take your time. You might want to stay away from other boaters until you get your control skills enhanced. One rule of thumb is the closer you are to the shore, the slower you go. Keep that prop out of rocks, trees, and debris that will ruin it and sometimes leave you stranded.
Did I say just take your time while you are boating? Have fun, enjoy your boat and make danged sure you let me know when you're going to be boating in my area, ok?:D
AMERICANS: Willing to cross a frozen river to kill you, in your sleep, on Christmas, totally not kidding, we've done it.