if you can't keep it up for more than a day or two, you're changing too many things too much. you don't have to eat perfectly healthy from day one. your only goal should be to be doing a little better than you were last week. small, gradual changes tend to be the ones that actually stick. it takes longer to get them into place [it can take six weeks to change just one habit], but once you take the time to actually change stuff you actually have to make an effort to change it back rather than just falling off into what you usually do.
if your marinated chicken breast taste bland, then my guess is that you aren't marinading them in the right thing. are you using spices? are you using enough of said spices? are you eating them plain or having a flavorful side with them. people who like chicken seem to love the spark slow cooker salsa chicken recipe, so that might be a place to start. what other flavors do you like? garlic? perhaps you could roast up a head of garlic, sautee up some greens like collards, mix in the roasted garlic and your bland chicken into the collards and enjoy that. and if you need some spice, adding some peppers [either fresh jalapeno or a dry spice like cayenne] would give you another flavor boost. you could also do a sage and brown butter sauce to drizzle over your plain chicken. or mushrooms and red wine. or peppercorns and cream. so make whatever sauce you used to love on chicken, just make a half batch and use it a little more sparingly than you used to.
what do you usually eat when you are off the wagon? what do you try and eat when you are on the wagon? if you would usually have sausage and eggs but are trying to switch to yogurt and museli, that might be too much for you. have sausage and eggs, but use a little less sausage and add some peppers, greens or broccoli to the eggs. if you would have a donut, try a bagel with cheese and maybe a piece of fruit.
if you share your old meals that you think need to be revamped, you can get some great suggestions for ways to revamp them or what other people who like those same types of things switched to.
-google first. ask questions later.