Of course you need to build up your confidence but getting on and off the bike when you see traffic will not help you. If it's 25 years since you cycled I reckon you must be an old sod of at least 36 but the same things applied then as they do now. Go slow enough and you fall off. Ride badly, dangerously or inconsideratly and you will come off worse especially with cars.
The best tricks I can sugest is to find a quiet place like a public park or maybe a trading estate with smooth roads / paths and have a poodlearound there building up your speed and stamina as you go. Then when you are a bit more confident ride on the roads but DO NOT,NEVER EVER get off when you see a car especially one behind you ( he's behind you, oh no he isn't) Just carry on cycling in a straightish line BUT GRADUALLY MOVE OUT ABOUT 2 FOOT FROM THE PAVEMENT.
The reason for this is simply this. You have given yourself an escape route if you need it. The arshole car drivers will eventually overtake you and sometime, just sometimes they cut in quick or driveclose to you to scare you. If they do this you have your 2 foot escape route to use but if you ride in the gutter all the time then when the drivers go too close to scare you you either have to jump up on the kerb or fall off. This is where the profanities come in handy,
The final bit of advice is to overtake parked cars in the middle of the road because many, many drivers don't look in their mirrors before they open their drivers door.
Wear a helmet and bright clothes oh and gloves because road rash really stings your hands.
Advice taken from years of experience, fights, Road rage, road rage, you ain't seen nothing till youv'e seen cyclerage!! hospital trips, busted helmets, torn clothes and a really good healthy set of lungs. Oh and this is from some old sod at least 14 years you senior
