I have met many folks who, like you, took lessons as a child and became proficient, but because of the negative aspects of a strict learning process that made learning the piano an academic process as exciting as learning algebra in school, they grew to loath the piano and stopped playing altogether. It wasn't fun it was work!
But, as Old John stated, you can learn piano or any other musical instrument at any age. And the good news is, that because you WANT to learn to play for your own enjoyment, and you won't have Atilla The Piano Teacher and/or your Dad criticizing your mistakes, you will find the learning process this go around, much less stressful.
The question is, how long do you want to devote to the learning process. In other words, as we get older, life gives us many other obligations that take up our time and it's more difficult to give priority to learning a non essential skill. By the time we get past age 30, we may have a job or career, kids, a spouse, many friends with whom we want to socialize or otherwise spend time, as well as other interest and hobbies.
Because of the time constraints due to other priorities in our lives as we get older, I would suggest that the approach to learning an instrument at an older age might be different than the process most children go through. In other words, when you took lessons as a child, you were probably learning some music theory, how to read music, as well as how to play right hand melodies and harmonies and left hand chords and bass lines. The learning methodology was likely based on the principle of slower learning and building upon skills that were incessantly practiced over and over in an effort to master each building block before moving on to the next.
As an adult, you may not have time to devote to that type of slow learning process. More likely, you are at a point where you want to develop the ability to play music on piano for your own personal enjoyment and to entertain your friends and you don't want to spend years devoted to long tedious practice sessions and lessons to get to that point.
If my assumption is correct, you might want to consider looking at some of the piano leaning systems that have been developed very recently that are based on technology that did not exist even ten years ago (my apologies in advance to the traditional piano teachers on Stake Exchange who are programmed to disagree). Keep in mind, this is just a suggestion for a possible alternative approach to learning to contrast more traditional methods There are limitations inherent in these programs, but they can get you playing some rather complex piano music in a matter of weeks vs. years going the traditional route. Many of the new technology based learning systems make the process fun, like playing a game. And using a system like the ones described below, won't bring back the negative memories associated with the lessons you were fearful of in the past.
Plus - as an adult who is choosing to learn the piano, you probably have the discipline to manage a self learning system without being forced to go to lessons by your Dad or piano teacher.
Keep in mind the shortcut methods are not geared towards someone who wants to make a career playing piano in a world renowned symphony orchestra but you could probably develop enough skill to play piano at Church, or even perform at a local pub or at fund raising events. They are geared more towards "instant gratification" than mastery as a skilled musician, but if you are like many adults who want to learn to play an instrument, you might be attracted to the "instant gratification" approach.
Some of your options might include the following:
Piano Suite Premier - According to their hype - "A comprehensive, interactive music learning, playing and composing system" It's a software based piano lesson system designed to help you learn without an instructor. Click this link to learn more Link to Piano Suite Premier
Synthesia - this is a learning system that is like playing the game Space Invaders that I played as a kid when video games first came out. You will not only learn to play songs on piano, but will have fun playing the games. You will need a computer or tablet and it works best with a keyboard that has MIDI capability. You can use an inexpensive "toy" keyboard like ones made by Casio and Yamaha, to learn the songs and transfer that learning to a regular piano. It does not teach timing in the traditional sense (learning to read music with quarter notes, and rests and time signatures etc.) but you can learn the songs at any speed and the music will playback with the appropriate timing for each song you are learning. Here is a link to discover more Link To Synthesia Website
Here is a link to ten different i-pad apps that are designed to help you learn to play piano or keyboard Link To Ten apps for i-pad
These are a couple of examples. There are also many keyboards with learning tools built in and many of those will also work in conjunct with a computer.
But a word of caution. Many of the technology based learning systems may actually hamper your ability to "learn" to "play piano". For example, the keyboards that light up the keys as you learn to play programmed songs, may allow you to play the songs, but you will be learning based on visually looking for the next light and pressing that key, and you may not even notice which key you are pressing. This type learning could prevent you from learning to form chords, and learning where the notes are in relation to one another.
If I were going to learn to play piano or keyboard with a software based learning system, I would look at the systems that allow you to wean yourself away from the shortcuts incorporated into the system. For example, if you use a program like Synthesia to learn to play a song, you will want to try to learn to play from memory, each song you learn to play using the system. Using that method won't teach you to be a musician or pianist per se, but it will allow you to quickly develop a repertoire of songs you can perform on piano.
For a more sustainable skill set that will allow you to advance your ability to play independent of software, and to fine tune technique, it would be advisable to take an occasional lesson of sorts from a qualified piano teacher who can evaluate your technique and keep you from developing habits which may limit your advancement as you progress.
Again, this is just a suggestion geared more towards folks who may come across this question in the future, but who might be too busy with adult responsibilities for the more tried and true traditional learning methods, but who want to be able to play some songs on the piano.
I wish you the best of luck with whichever direction you go with re-learning the piano. Most importantly, keep it fun!