The Ukrainians have absorbed the initial shock of invasion day. They have acquitted themselves well and inflicted a toll on the invader.
The most important thing now is not the volume or even quality of their engagements with the Russians, it is to keep an army in the field. If they can keep a regular Ukrainian force in the field, then ANY successful counterattack, no matter how militarily insignificant, will be electrifying to the whole world and provide a jolt to morale for the irregular fighters as that fight begins to materialize. The West can help the Ukrainians by amplifying the signal of any military success, regardless of significance. The will to fight is the center of gravity. The heroic defenders in the Ukrainian armed forces have given their country a fighting chance so far, at great cost to themselves.
Taking an even more macro perspective, even if the Ukrainian soldiers all go down swinging and were to lose this fight, their heroism will provide a foundation for the Ukrainian national identity to reassert itself in the future based on the deeds of their martyrs, e.g. the Irish rebellion of 1798 (to name one) .. they didn't win in their own day, but their descendants were still singing songs about them when they finally evicted the brits over a century later.