I'm getting back into biking and sometimes feel a bit as you've described, though it's lessening all the time. A couple of suggestions:
- start with rides you find easy, on roads you're familiar with
- ride with a friend or a beginner group if you can find one
- wear a high viz jacket or vest so you know other traffic will see you easily
- get someone to show you how to change a tube, practise at home until you're confident, and always carry a spare tube and tire levers with you (seatbag is usually the easiest place to put them, then they're there on the bike all the time). Changing a tube really isn't a big deal once you know how.