Difference between Be on the mend and Mend one’s ways

be on the mend—

1. be getting better after illness:

• He has been on the mend under the excellent care by his wife Phyllis.

2. (of things) improve:

• The economy has been on the mend since the data in the report was gathered.

mend one’s ways—improve one’s behavior, work, etc.:

• He is unlikely to mend his ways unless he is forced to do so.