It's a natural human instinct we simply cannot escape - this is why, for instance, your reflexes instantaneously move your hand off a hot stove before it begins to burn, because your mind's job is to keep you out of harm. This also means that to succeed in swimming (and life) we must do one of these two things; we must enjoy what we do, or otherwise, we have to find a WAY to enjoy it.
So if you are not enjoying your swimming, it is essential to ask yourself why - and change 'whatever it takes' to get yourself back in the successful 'Happiness Club'. If you want to succeed, get happy! Unhappiness, time and time again, has proven to bring failure, because it simply affects every major area of a swimmer's life - their emotional balance, motivation, perseverance, their relationships with coaches and other swimmers, and every other aspect of their training.
Some major reasons for unhappiness I've come across with swimmers I've worked with included: boredom and lacking variety in their training, a personality clash with a coach or other swimmers in their squad, and being stressed out time-wise through other commitments such as work, school, family and social life.
These are all things which can arise in everyday life, however they are also things which can be fixed! There simply isn't a problem which can't be fixed completely or improved in some way - the key is to look for the answers. Personality clashes are a classic example. Successful people take responsibility for their own happiness, they don't rely on everyone else to be nice to them before they can enjoy themselves. Champions rise above these situations and decide that nothing is going to get in their way of what they want - they must either fix these personality clashes, or get away from them, so they can focus and swim in a more positive, enjoyable environment. This is not to say that these problems are not valid concerns - they are! And that is why they should be treated and fixed quickly, before you find your motivation beginning to become affected - this is what all swimmers should do when faced with a problem.
If you ever begin to feel that you're losing your motivation, ask yourself why. If it has to do with your training, or a personality clash, talk to your coach and discuss it with them, to see if her or she can help. If it is your busy schedule, sit down and write out a new one, and see if you can fit in a little more relaxation. Life is too short not to enjoy what you are doing, and once again, if you really wish to succeed, your enjoyment is an essential ingredient - a plain and simple fact.
Put your own personal happiness at the very top of your priority list - and never, ever let it drop below number 1. Your motivation must always be there before you can make any serious attempt at achieving any goal. This does not mean that you'll enjoy every waking second of your life (there will always be some areas which are not as enjoyable as others), but the main thing is to overall enjoy what you do. This applies to your life just as much as your swimming!
If you love your swimming, then you're in the driver's seat - and you can't go wrong. Don't change a thing! But if you don't, find out why, and fix it. Never let anyone, or anything, affect your motivation - because this is the very thing that gets you out of bed every morning!
Protect it, treasure it - because it's an essential part of who you really are.