As a nurseryman I occasionally get asked by customers what to do about a plant that is unhappy in its current location. I try to determine the reason for its difficulty and this is usually one of four things:
1. The plant is either getting too much sun (because it's a shade lover) or too little sun (it needs some heat).
2. The watering schedule doesn't match the plant's needs (too little or too much). If the soil wasn't adequately amended and the roots are wet all the time that can lead to a slow demise.
3. The plant is besieged by insects that are causing it harm.
4. The plant is nearing the end of its natural lifespan.
Some of these problems can be resolved. If it's a watering/drainage issue, a new schedule can be implemented. If it's insects, organic sprays are available, though one has to attend to what is causing the plant to be susceptible to the insects in the first place (healthy plants usually resist disease and insects).
The first scenario listed above does sometimes involve moving the plant and customers are rightly apprehensive to undertake this. Plants don't generally like to be disturbed. However, if conditions have changed -- say a tree offering shade was cut down exposing a shade loving plant to considerably more sun -- gardeners may have no choice but to move it. I always advise that it's better to move it than let it struggle in the new adverse conditions. If the rootball is protected, most plants can be moved. This gives you the chance to provide it ideal soil conditions in its new home. And sometimes gardeners need to move a healthy plant if they're redoing a planting bed.
The last scenario, the plant is nearing its end (or is very weak) is always hard but if a plant is unlikely to rebound to full health, sometimes it's better to start over with a new specimen or to plant something else in that spot. And plants do have a natural lifespan.
My favorite example is a customer who came into our nursery, sad that his daphne plant seemed to be doing so poorly. After running through the usual questions, I finally thought to ask him how old the shrub was. When he said 20 years I nearly snorted. "Twenty years?" I said, incredulous. "Daphnes usually only last 5-10 years. Consider yourself very lucky." Customers are rightly relieved to be told that they have done nothing wrong when the answer is that the plant in question has simply reached its natural end.
I share these thoughts because the goal of all gardeners is to have healthy, vibrant plants. Sometimjs we need to do things to improve their health but there are times when we need to move them or simply start over. And that's okay.