There is definitely a mental component. If you decide you're not going to like broccoli - you will surely hate it. I compare anal sex to alcohol or cigarettes - the first time is usually not pleasurable - but with some positive reinforcement and the desire to 'succeed', you'll likely learn to like - even love it.
I have found that along with lots of patience and lube - tapered toys are extremely helpful in learning to relax as your anal muscles dilate.
After 23+ years of 'no' - my wife is now comfortable with anal sex and is beginning to find some enjoyment in it.
Good luck - and add more lube!!!