We have no way of knowing (research has not been done) whether a happy transitioner would have been happier in the long run had they not transitioned. One thing we do know for certain is that they would, assuming transitioners medicalise, be healthier.
Happiness on transition is short-lived – sometimes called ‘gender euphoria’. Regret might be temporary as one comes to terms with things. However, harm, scars, sterility, premature aging, they are all permanent.
Detransition is more common than proponents of transition would have you believe.
In terms of public health, it is reasonable to equate transgender ideation with smoking.
Best not to start. Give it up before it limits your life.