The definition of resent from Merriam-Webster Online is: to feel or express annoyance of ill will at. This usually involves an intention toward past equilibrium and away from present and future balance. You see this a lot in relationships. One might say, "Why can't things be the way there have always been"? What they are asking for is impossible but they need to see that they are asking the impossible before they can see that their non-acceptance of the present person is preventing their acceptance of the present moment, and their precipitating the holding on to their resentment.
In depression one has a deep and enduring resentment toward the current self. The intention is to sabotage any chance for current contentment. This intention is typically fueled by an intention towards the past. This intention towards the past is fueled by an intention towards balance. The individual is spending a great deal of time thinking of the past, either trying to get back to a time of former balance, or trying to change events that threaten present self acceptance. For example the individual is trying to get back to who they were before a major loss of self balance effected by a trauma or series of traumas. Or the individual is trying to find out how they could have prevented past trauma by reviewing it over and over again. In both cases the intention is to go back in time to change things. Present happiness will always be denied, even though it can't help but happen in the moment.
Don't spend too much time in self reflection.
Don't beat yourself up.
Don't tell yourself: "I can't feel this".
Don't self medicate
Do---Notice your mental tendency to hold onto your depression.
Do---Create an intention toward movement.
Do---At least once daily connect to this moment with intension and acceptance. Depression is nearly always an unconscious intention towards the past. We must counter this with a conscious intention toward this moment. We need to find ways to momentarily suspend our ideas, our judgments, and our desire to be somewhere else, and just be here. Start with relatively easy things. You can watch the sky with the intention of really seeing it. You can listen to someone with the intention of just listening. You can pet your dog just with the intention of petting your dog. You can walk just with the intention of just walking. But, no matter what be as conscious and aware as you can be. See everything that you can with intensity. Don't let your awareness to be narrowed and closed, try to see the object in front of you with focus but also see everything in your periphery in as much detail as possible, see all there is to see. Also do this with your other senses. Hearing, hear all that is there, smell what there is to smell, and really taste that which you are tasting.
Do---Go see a therapist. Depression is usually very treatable, and a good therapist will be able to help you find your stuck places and help motivate you toward movement.
Do---Consider taking medications prescribed by a doctor. Know that this is not a cure but it is a way to be able to function while you are working with a therapist.